This presentation will deal with the development of new synthetic strategies and tactics associated with polycyclic compounds, an important structural motif in many biologically active natural products. One of the key points is the regioselective [2+2] cycloaddition of ketene silyl acetals and benzynes, which serves as a basis for the selective construction of phenylnaphthalenes, a common structure embedded in various natural products. Also discussed will be a class of structurally intriguing unnatural products, i.e., dicyclobutabenzenes and tricyclobutabenzenes.

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Cavity-directed chemical transformations represent one of the most important features of three-dimentional hosts, but yet have been less explored in previous synthetic receptors. We are developing such functions with the large cavity of the self-assembled cages, particularly an M6L4-type cage complex shown in the Scheme. The photodimerization of olefins in this cage is featured, for example, by remarkable rate enhancement (>102 times), perfect regio- and stereo-selection, and high pairwise selection (when two different olefins are used) giving only a cross [2+2] adduct. Another intriguing property of the cavity is the stabilization of labile molecules by encapsulation. We succeeded in trapping a labile molecule by preparing it in situ from small components coming through small portals of the cage. Cavity-sensitized photochemical reaction as well as endohedral clusterization of water molecules in the cavity will be also discussed.

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Singlet diradicals are important intermediates in processes involving bond-formation and bond-cleavage. However, so far, the singlet diradicals are only the putative intermediates due to the short-lived species. Recently, we have found the singlet ground state and the log-lived singlet 2,2-dialkoxy-cyclopentane-1,3-diyls. The singlet ground state is explained by the hyperconjugative stabilization of the lowest singlet state. In the present study, the regioselective 1,2-oxygen migration was observed for the unsymmetrically substituted diradicals, which clearly supports that the hyperconjugative resonance structures are included in the singlet diradicals.

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To disclose the property of the oxatetramethyleneethane (OTME),
an oxa analogue of tetramethyleneethane,
we carried out DFT or ab initio calculations of the parent or
aryl-substituted OTME, and product analyses or spectroscopic studies of
the aryl-substituted OTME.
In this presentation, we will discuss the molecular geometry and
electronic character of the parent or aryl-substituted OTME.

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The present paper deals with a new isomerism of cation radicals. Thus, the DFT computational studies with B3LYP/6-31G(d) level theory have been carried out for hydrocarbon cation radicals such as triphenylmethane cation radicals and its proton-migrated isomers in which the benzyl hydrogen has migrated to the carbon atoms of the benzene rings. Similar calculations have also been performed for alkene and alkyne cation radicals containing a benzylic hydrogen and their corresponding isomers in which the benzylic hydrogen has migrated to the alkene or alkyne carbon atoms as well as those of benzene rings. We have found that many hydrogen-migrated isomers of the hydrocarbon cation radicals are more stable than their corresponding parent hydrocarbon cation radicals. The results may be interpreted in terms of extended conjugation of spins and charges through the mixed conjugated system which is created by the generation of trivalent benzylic carbon in the isomeric molecules.

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Reaction of singlet oxygen with the naphthalene 1 containing lactic acid side chain gave a diastereomeric mixture of hydroperoxides. The stereoselectivity depends on the concentration of the substrate 1 and reaction temperature. We propose that the stereoselectivity is controlled by hydrogen-bonding association of the substrate 1 at the higher concentration of 1 and at the lower temperature. A major isomer of the product forms via anti-relationship between singlet-oxygen addition and carboxylic-acid addition to naphthalene stereoface. The association of the carboxylic acid side-chain may induce steric hindrance to result in the anti-addition. Proton NMR chemical shift of 1 depends on the concentration of 1 and temperature, and these dependencies can be explained by the association of the carboxylic acid.

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Endohedral metallofullerenes encapsulate one or more metal atoms inside a hollow fullerene cage.The functionalization of paramagnetic endohedral monometallofullerene is of interest for their application as new types of organic ferromagnets, etc. We report here an isolation and crystallographic characterization of a paramagnetic endohedral monometallofullerene derivative from the selective La@C₈₂-A-carbene reaction.

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Stable benzene trimers with a large binding energy have been observed, and theoretical calculations have predicted a C₃-symmetric cyclic structure. The binding energy of the benzene trimer has been reported to be 6.2 kcal/mol, as determined by a gas phase experiment. This large binding energy could be attributable to the three concurrent cyclic CH/π interactions. We found a closely similar structure with three benzene nuclei in the title compound, which should have the same CH/π stabilization as the benzene trimer. The structure has been proved by the Xray crystallography, the theoretical calculations and the dynamic NMR measurements, which also shows the thermodynamic stability of the observed C₃-conformer. We will discuss the structure of the title compound in the relation to the stability of the benzene trimer.

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The origin of facial diastereoselection has attracted active debate and most arguments were, as typified by the Cieplak model and the Felkin-Anh model, based on the premise that transition state stabilization be essential. However, we found that observed diastereoselectivities in LiAlH₄ reduction of α-substituted-ketone are exactly opposite to the predictions made by the Felkin-Anh model. Moreover, ab initio calculation showed that the transition structures are quite different from that suggested by the Cieplak model. Structural analysis of optimized transition states has revealed that coordination of both carbonyl and methoxy oxygen atoms to lithium significantly stabilize transition states and largely affect the selectivities. In addition, IRC calculation suggested that the coordination has been already arisen at the initial stage, which cause difference in the accessibility of hydride between two carbonyl faces.

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Photolysis of diazo ketone is one of the popular method to generate ketenes. We are intersted in the effect of aza-aromatic derivatives which may be effective on the formation of ketenes and their reactivities. Our studies carried out with using laser flash photolysis with the detection of UV-visible and infrared spectroscopy.Hydration and amination of ketenes which were formed by laser irradiation were influenced by the basicity of the nitrogen atom. The lone pair electrons of the nitrogen captured intramolecularly the first formed ketocarbene and ylide compounds are formed.

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9,10-Phenanthrenequinone (PQ) forms 1:1 complexes with metal ions (Mⁿ⁺ = Sc³⁺, Y³⁺, Mg²⁺, and Ca²⁺) in acetonitrile (MeCN). The binding constants of PQ–Mⁿ⁺ complexes vary depending on both the Lewis acidity and ion radius of metal ions. The one-electron reduced species (PQ^•–) forms 1:1 complexes with Sc³⁺, Mg²⁺, and Ca²⁺, whereas PQ^•– forms 1:2 complexes with Y³⁺ and La³⁺, as indicated by ESR measurements. Rate of electron transfer from CoTPP (TPP^2– = dianion of tetraphenylporphyrin) to PQ increases with increasing the concentration of Sc³⁺ to reach a constant value, when all PQ molecules form the 1:1 complex with Sc³⁺.

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Mechanistic investigation on the 9,10-dicyanoanthracene (DCA)-sensitized photoreaction of triarylphosphines in acetonitrile under aerobic conditions was carried out. Product analysis by GC shows that was oxidized to the corresponding phosphine oxide with no appreciable side reactions. Certainly, the reaction is initiated by electron transfer from triarylphosphine to DCA in the singlet excited state with the aid of co-sensitizer, biphenyl, giving the triarylphosphine radical cation. On the other hand, laser flash photolysis experiments reveals linear dependence of decay rate of the triarylphosphine radical cation on the concentration of molecular oxygen, suggesting that the radical cation reacts with the oxygen to eventually afford triarylphosphine oxide. Most likely, triarylphosphine radical cation undergoes radical-attack on oxygen in the ground state in this photoreaction.

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Stereoselectivity in photoallylation and photoreduction of acyclic electron-deficient alkenes by allylic silanes was investigated. The photoallylation and photoreduction proceed via photoinduced electron transfer, and the progress of the photoreactions was accelerated by the addition of carboxylic acids. Diastereoselectivity of the reduction product in the photoreaction of 1,1-dicyano-2-methyl-3-phenyl-1-butene increased up to 72% when 1 equivalent of L-lactic acid based on the alkene was added. Enantioselectivity of the photoreaction was examined by use of 1,1-dicyano-3,3-diphenyl-1-propene as a substrate. When 1 equivalent of (R)-mandelic acid based on the alkene was added, allylated product was obtained in 3.4% ee.

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The reactions of 4-silatriafulvene 1 with ketones are investigated. At rt, three types of reaction modes are observed. (1) Good enophilic arylketones are immediately reacted with 1 to give [4+2] adduct by a concerted mechanism. (2) Good electrophilic enones such as cyclohexenoe are reacted with 1. (3) Poor electrophilic aliphatic ketones such as acetone and adamantanone are not reacted with 1. We have found that 1 gives silacyclobutadiene 6 at 80 °C. Low reactivity of 1 toward less reactive ketones allowed us to investigate the reactions of 6 with ketones at the higher temperatures. At 80 °C, the reactions of 6 with aliphatic ketones occur. The unsaturated silicon of silacyclobutadiene 6 serves as an electrophile toward the aliphatic ketones similarly to that of a usual silene. The reaction of 1 with di-tert-butylcyclopropenone generated a highly strained 5-silabicyclo[3.2.0]heptatriene derivative.

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The 1,3,6-Triphosphafulvene showed regioselective reactivity toward alkyllithiums at the external phosphorus atom to afford the corresponding phosphinodiphospholide anions. The diphospholide anions were allowed to react with alkyl halides to yield the corresponding phosphinodiphospholes. On the other hand, the generated phosphinodiphospholide anions were allowed to react with acetic acid to afford the diphosphacyclopentadienylidenephosphoranes, which are phosphorus ylides bearing a P-H bond. Alternatively, reaction of the 1,3,6-triphosphafulvene with tetrafluoroboric acid afforded the phosphorus ylide bearing a P-H bond. The structure of the phosphorus ylide was analyzed by crystallography and was discussed. Additionally, we studied reactivity of 6-phosphafulvene to compare with the property of 1,3,6-triphosphfulvene. Furthermore, a 3,4-dihydro-1,3,4-triphosphacyclopenta[a]indene was isolated in the reaction to obtain the 1,3,6-triphosphafulvene.

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Treatment of dichloroferrocenylphosphine with two molar amounts of a lithium phosphide bearing 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl (denoted as Tbt) group afforded the corresponding 1,3-dihydro-2-ferrocenyltriphosphane [1; (TbtHP)₂PFc, Fc = ferrocenyl] in 73% yield. The structural characterization of 1 was achieved by the NMR spectra and X-ray crystallographic analysis. In the ³¹P{¹H} NMR spectrum of the mixture of three diastereomers of 1, the characteristic two A₂B and one ABX systems were observed as signals assignable to two meso and one dl isomers, respectively. Thermolysis of 1 in toluene led to the quantitative formation of TbtPH₂ and (E)-TbtP=PFc. Kinetic studies indicated that the thermolysis of 1 is the first-order reaction including a unimolecular dissociative process, which was reasonablely supported by theoretical calculations.

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We have already reported the syntheses and structures of 6-carbaphosphatrane 1 and its tautomer 2. We report here the reactivities of 1,2 as well as those of 5-carbaphosphatrane 5. The apical hydrogen atom of 1 was replaced by a deuterium atom by the reaction of 1,2 with methanol-d₁. This reaction proceeds through a proton exchange of 2. Treatment of 1,2 with Ph₃CClO₄ afforded a phosphonium cation 3 which was generated by a hydride abstraction from 1. Such reactivities are caused by changing of the property of the hydrogen atom of 1 and 2 via the tautomerization. Photoreaction of 1,2 with catalytic amount of PhSSPh afforded phosphonate 6 bearing a toluene moiety. We also investigated various radical reactions and these reaction mechanisms will also be described.

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Recently we succeeded in the synthesis of thermodynamically unstable anti-apicophilic pentacoordinate spirophosphorane with a Martin ligand to the corresponding O-apical stable isomer. But, the p-Me O-equatorial compound is easily isomerized. Therefore, we synthesized o-C₆H₅C(Li)(C₂F₅) ₂OLi. The dilithiated compound was successfully used for synthesis of O-equatorial p-Me compound. Although the p-Me O-equatorial compound is stable at room temperature, it was isomerized to its stable isomer with O-apical arrangement upon heating. Kinetic measurements for the isomerization were carried out by ¹H NMR to determine the activation parameters of the isomerization. Moreover, the synthesis of hexacoodinate phosphate bearing the ligand will be discussed.

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Metastable ion spectral data based upon electron ionized molecular ions for titled compounds (25 species) have been summarized measued by a double reversed geometry four sector tandem mass spectrometer focussed in single/double hydrogen transfer from &omega-phenylacyl group into (thio)lactam moiety by either deuterium labeling or carbonyl/thiocarbonyl functions.

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Alcohol molecules in water form self-association clusters through hydrogen-bonding interaction. This has been explained by the hydrophobic interaction. Therefore, the hydrogen-bonding network of water is thought to coexist with the alcohol clusters. However, by the mass spectrometric analysis of clusters in solutions, the new insights were provided as follows: (1) When the formation of alcohol clusters was promoted in water, hydrogen-bonded water clusters were not formed, (2) The alcohol self-association clusters were generated by the mixing with acetonitrile and dichloromethane as well as with water. The self-association of alcohol is found to be promoted by the mixing with the solvent which is difficult to solvate alkyl group of the alcohol.

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The stability of ions in solutions is dependent on the solvation effect, which is governed by the interaction properties of solvents. However, the stability of carbocations and carbanions in organic solvents has been quantitatively estimated by using of the stability scales in aqueous solvents. Therefore, the stability scales in aqueous solvents cannot always successfully be applied to the estimation of the stability in organic solvents . This time, we have comparatively examined the stability scales for carbocations and carbanions in organic solvents and in aqueous solvents on the basis of those in gas phase and solvation energies in the solvents.

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Substituent effect on the acidities of phenols in water is considerably different from that in gas phase. That is, acidities of phenols which have electron-withdrawing groups at the para position are intensified in comparison with that in gas phase. In order to make clear the origin of this phenomenon, ab initio calculations were done. Energies of substituted phenoxides and corresponding phenols were calculated to determine relative acidities in gas phase for phenols. In addition, energies of corresponding species, which are specifically hydrated in some manner, are also calculated. Some kinds of relative acidities of phenols, which include specifically hydrated components, were determined. Their substituent effects were compared with that in gas phase and experimental one in aqueous phase. It was developed that the specific solvation to the ring substituents of phenoxides by one water molecule is the intrinsic factor to reproduce the acidities of phenols in water media.

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Kinetic effects of pressure on the title reaction were studied. The reaction was insensitive or slightly retarded to a change in pressure at P < 120 MPa. However, it was accelerated by an increase in pressure at P >150 MPa, showing the existence of two reaction routes with and without solvent participation. At higher pressures, viscosity-induced retardations were observed in highly viscous media. Since these retardations of the reactions were observed only at high viscosities, they were taken to indicate a failure of the transition state theory caused by slow solvent thermal fluctuations. The analysis of the dynamic solvent effects on the basis of two-dimensional reaction coordinate model will be discussed.

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Reports on experimental studies on Cp cations are quite limited due to their intrinsic instability because of the antiaromaticity. Annelation of rigid cycloalkene framework(s) would be an effective way to stabilize such labile pi-conjugated cationic species. We report here the generation and reaction of a new phenyl-substituted Cp cation, annelated with two homoadamantene frameworks. The Cp cation was generated using a newly synthesized chloride as a precursor either by i) methanolysis or ii) abstraction of chloride ion by Ag+ or B(C6F5)3 in dichloromethane. The methanolysis gave a methyl ether corresponding to the starting chloride, as a result of capture of the intermediate Cp cation by a solvent molecule, whereas under the latter conditions the Cp cation underwent Wagner-Meerwein rearrangement of the homoadamantene framework to avoid antiaromatic destabilization and subsequent intramolecular cyclopropanation, giving a stable allyl cation.

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The conversion of oximes into amides, known as the Beckmann rearrangement involves an initial protonation of an oxime to oxonium cation followed by a migration of an anti-group and departure of water molecule giving a nitrilium cation, which upon hydrolysis yield the final amide product. Certain oximes, particularly those having a quaternary carbon anti to the hydroxyl, are likely to undergo fragmentation to form nitriles instead of amides. In the present study, we have carried out ab initio MO and MD calculations as well as experimental analyses on the rearrangement reactions of oximes to address several important mechanistic issues; (i) Are these reactions follow a stepwise or concerted pathway? (ii) Do the fragmentation and rearrangement products share a common intermediate? (iii) How does the change in reaction pathway occur?

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Kinetic and equilibrium studies of the reaction between aromatic amines and activated aromatic substrates were undertaken in cyclohexane as well as in benzene. Currently prevailing mechanism of the nucleophilic aromatic substitution (S_NAr reaction) is the one with a steady-assumption on the first intermediate, Meisenheimer complex.
In the present study, NMR investigations show no NMR chemical shift change takes place on the change of aniline concentration in cyclohexane thus negating the presence of the aniline dimer in cyclohexane, and also show a possible dimer formation in benzene is not significant to warrant an intervention in S_NAr reactions.
With the absence of effective dimer formation of amine in typical nonpolar solvents, the operation of "Amine-Dimer Mechanism" should not be considered in these solvents and the operation of "Steady-State Mechanism" should be considered unappropriate.

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In the last decade, we reported the substituents effects at C(2) on the ground state spin multiplicity of localized 1,3-diradicals and proved electron-withdrawing substituents (X = F, OR) allow to locate energetically the singlet states below the triplet states. The lifetime of the singlet diradicals is short at room temperature, since the intramolecular cyclization and migration reactions of substituents at C(2) are fast. Now we have designed 2-heteroatom-substituted cyclopentane-1,3-diyls (M = Si, Ge) to retard the rates of the intramolecular cyclization and 1,2-migration. Thus, the strain energies of heteroatom-substituted cyclopropanes are higher than that of cyclopropane and the π-bond energies of CH₂=MH₂ are smaller than that of ethylene. We also found the ground state spin multiplicity of localized 2-boracyclopentane-1,3-diyls (M = B) is singlet state. We have tried to isolate the 2-silacyclopentane-1,3-diyls experimentally.

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In the past decade, we have investigated substituent (X) effects at C(2) on the ground-state spin multiplicity of cyclopentane-1,3-diyls DR1 (Y = H), and found that the ground-state spin multiplicity of 2-alkoxy (X = OR) or 2-silyl (X = SiR₃)-1,3-diyls is singlet state. In this study, we investigated computationally the singlet-triplet energy gap in 1,3-diyls that possess electron-withdrawing (DR2, Y = CF₃) or donating group (DR3, Y = OMe) at C(1) and C(3). Consequently, we found that the energy gap in DR2 (X = OMe, Y = CF₃) was calculated to be smaller than DR1 (X = OMe, Y = H). Alternatively, the energy gap in DR2 (X = SiH3, Y = CF3) was computed to be larger than DR1 (X = SiH₃, Y = H). In the diradicals DR3 (Y = OMe), however, we found that the energy gap of 2-alkoxy-substituted diyls is calculated to be larger than DR1. It should be noted that the 2-silyl-substituted diradical DR3 was calculated to be the triplet ground state moles.

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Denitrogenation of azoalkanes is known to be an efficient method not only to generate radicals, but also to synthesize strained molecules. For example, the denitrogenation of 1-pyrazolines produces cyclopropane derivaties in high yields. However, for the denitrogenation of 3-electron-withdrawing group-substituted 1-pyrazolines, the main product is not the intramlecular cyclization product but a rearrangement product. In the present study, the substituent effect that control the product distributions was investigated with a combined experimental and theoretical studies.

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We previously reported the photoinduced electron-transfer (PET) degenerate methylenecyclopropane (MCP) rearrangement of diarylmethylenecyclopropane (1). The reaction proceeds via two different types of intermediates, a trimethylenemethane (TMM) radical cation (2 radical cation), and TMM biradical (2-biradical). The MCP rearrangement of 1 was also triggered by g-ray irradiation in a low temperature glassy matrix. The most characteristic feature is that the intense thermoluminescence (TL) was observed on the annealing of the sample matrix. Spectroscopic studies and energetic analyses suggest that the TL is originated from the excited state of TMM, (2-biradical)*, which is generated by electron-transfer (ET) reaction of 1 followed by bond cleavage and charge recombination. A potential application of the ET reaction of 1 toward organic electroluminescence will be also discussed.

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In the present study, stereoselectivities were examined in the PD-tethered reaction of the diazo compound synthesized from (R,R)-2,4-pentanediol and catechol in four steps. When the rhodium catalyst was added to a CDCl3 solution of the diazo ketoester at room temperture, cyclic ether products were obtained in a 76% yield. The diastereomer excess (de) of the intramolecular O-H insertion was 84% at highest. Kinetic protonation of the enolate generated from the product gave the product mixture of isomer ratio up to 30:70. This kinetically protonated product was isomerized with acetic acid and DABCO to give the thermodynamic mixture, which is similar to that obtained by the O-H insertion reaction. That is, the stereoselectivity of the O-H insertion is close to that controlled thermodynamically. However, it was confirmed that the isomerization of the product did not occur under the reaction condition. The stereoselectivity must be controlled at the later stage of the reaction.

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Substances showing insulator-to-conductor conversion by irradiation of light may have a potential for novel highly functional materials. Our purpose of the study is to develop a novel photochemical doping reaction for generation of electrical conductivity. Tetrtacyanoquinodimethane(TCNQ) has been known to show electrical conductivity upon partial doping of electrons. If TCNQ is doped by a sacrificial donor which releases electron irreversibly by photochemical reactions, photo-generation of conductivity is expected. The Langmuir-Blodgett (LB) technique was employed in this study, which has been used to fabricate thin-film molecular assemblies. LB films prepared as alternating layers of octadecyl-TCNQ and the donor on interdigitated array electrode, upon photo-irradiation, showed conductivity by the doping reaction.

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It has been known that photo-irradiation of substituted norbornadienes leads to the one-way isomerization to highly strained quadricyclanes which undergo the reverse isomerization by electron-transfer sensitizations. Therefore, the photochemical pathways can be switched depending on the presence or absence of photosensitizers, which may be controlled by the reaction media where the sensitizers are dissolved. Such situations may be achieved with COOH-substituted norbornadienes and quadricyclanes when one of two isomers has a higher acidity and is soluble in water at an appropriate pH. Thus, the properties of such carboxylic acids were examined, and quite large difference in acidity by about 1.5 pKa unit was found for some norbornadiene and quadricyclane derivatives. Using these substances, photocontrol of interfacial mass transfer between organic and aqueous layers has been achieved, which may lead to novel flip-flop type photochromic systems.

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The effects of a catalytic amount of PhSH on the intramolecular triplet photocycloaddtions of three phenyldicyclopentadienones 1, 2 and 3 (9-phenyl, 8-phenyl and 5-phenyltricyclo[5.2.1.0^2,6]deca-4,8-dien-3-one, respectively) were examined. While the reactions of 2 and 3 were remarkably accelerated by PhSH, but the reaction of 1 was not influenced. The triplet energy profiles depicted by DFT calculations revealed that the formation of triplet biradicals from the styrene moiety triplet is largely exothermic for the reaction of 1, but endothermic for the reaction of 2 and 3. This agreed with the facts that the reactions of 2 and 3 were extremely slow compared to the reaction of 1. The theoretical results suggest the possibility of the spin inversion of the triplet biradical to the ground state singlet to be the rate determining step and the catalytic assistance of this step by PhSH.

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Photoirradiation of a methanol solution containing 2,5-dimethyl-2,4-hexadiene (1) and 9-cyanophenanthrene (9-CP) is known to give oxidative photodimerized product, 2,9-dimethoxy-2,5,5,6,6,9-hexamethyldeca-3,7-diene (2), via photoinduced electron transfer reaction. In this work, we examined about the mechanism of the oxidative photodimerization reaction, improvement of the efficiency, and application to the organic synthesis. As a result, we found that the photodimerization reaction is efficiently catalyzed by 9-CP to give 2, and that various nucleophiles can be introduced to the dimerized products.

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Photoinduced electron-transfer reactions of 1,2-bis(α-styryl)benzene (1) gave the corresponding cyclized product, an o-quinodimethane derivate (2). Time-resolved absorption spectroscopy upon laser flash photolysis of 1 confirmed that 2 radical cation decayed and 2 rose with nearly the same rate constants. These results provided the first agreement in kinetics between a reactive radical cation intermediate and the corresponding neutral species formed by back electron transfer.

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o-Benzyloxy-benzyl acetate(1) is expected to form benzyl cation and acetate ion pair due to the zwitter ionic resonance structure of quinine methide. The photochemical formation of the ion pair was investigated in CD3COOD by the aid of ¹H-NMR supectrum and HPLC.o-Hydroxy-benzyl acetate (2 55.9%) and benzaldehyde (3 65.6%) were obtained after 3h irradiation suggesting the homolytic cleavage of ether bond of 1.No heterolytic cleavage of ester bond of 1 was shown by the absence of external return of CD₃COOD or CD₃COO^-.

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Photosolvolysis of 2-chloro-3-phenylpropiophenone(1) was investigated in 2,2,2-trifluoroethanol. 2,3-Diphenylpropionic acid trifluoroethylester(2), 3-phenyl-2-trifluoroethoxypropiophenone(3),2-phenyl-3-trifluoroethoxypropiophenone(4) were identified by the aid of ¹H-NMR spectrum and HPLC. The substituents on 3-phenyl group greatly affected the photosolvolysis products. Photo-Favorskii rearrangement was facilitated by the electron-withdrowing substituent, while the rearrangement was completely surpressed by the electron-donating substituent. These results suggest that phenacyl cation is formed by the electron transfer from 3-phenyl ring and Photo-Favorskii rearrangement undergose through the phenacyl radical.

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We have found that both benzhydrol and benzpinacol were obtained as major products in the photoreaction of benzophenone and 1,3-dimethyl-2-phenylbenzimidazoline (DMPBI), and their yields markedly varied depending on the kind of proton donor. On the other hand, in the photoreaction of benzophenone and 2-hydroxyphenyl-1,3-dimethylbenzimidazoline (HPDMBI), benzpinacol was a major product regardless of the reaction conditions. In order to investigate further photoinduced electron transfer reaction mechanism of DMPBI or HPDMBI with benzophenones, we conducted photoreaction of 3-methylbenzophenone as a probe substrate under the various reaction conditions. We also explored the properties of the oxidation products derived from DMPBI and HPDMBI.

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We have already discovered that the reaction of alkoxycarbonyl substituted ketones (RCO-COOR') with samarium diiodide (SmI₂) gave samarium ketyl radicals that underwent intramolecular ketone-ester coupling reactions followed by rearrengements to afford various cyclic alcohols. To investigate the generality of this ketone-ester coupling reaction, we conducted the reaction of acyloxy substituted ketones (RCO-OCOR') with SmI₂ and found that intramolecular ketone-ester coupling reaction also proceeded to produce 2,3-dihydroxy cyclic ethers. We will present the detailed experimental results and discuss the reaction mechanism.

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We investigated the glycosidation of 2-acetoamido-3,4,6-tri-O-benzyl-D-glucopyranosyl acetate using the combined activators of ytterbium (III) trifluoromethanesulfonate-3 mol% boron trifluoride. The reactions using aromatic alcohols stereoselectively gave the corresponding aryl α-O-glycosides. And the reactions using alcohols afford the alkyl β-O-glycosides. The species of acceptors remarkably changed the stereoselectivities of the obtained glycosides, which was not found in the conventional glycosidations of N-acetyl-D-glucosamine derivatives. We speculated that the novel glycosyl intermediate, which was influenced by ytterbium metal, would be generated from N-acetyl-D-glucosamine derivatives.

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The reaction of 2,3,4,6-tetra-O-benzyl-1-C-vinyl-D-glucopyranose with several nucleophiles in the presence of Lewis acids was investigated. When allyltrimethylsilane and silyl enol ethers were used as the nucleophiles, we found that the reaction conditions using 20 mol% TMSOTf promoted the S_N1' reaction to afford the corresponding exo-(Z)-glycals, which was caused by the attack of the nucleophiles to the terminal olefinic carbon atom in the glycosyl cation intermediate.

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Thermochromism of metal ion complexes of semiquinone radical anions vary depending on metal ions. Metal ion complexes of 1,10-phenanthroline-5,6-dione radical anion (PTQ^•–) produced by the electron-transfer reduction of PTQ by 1,1-dimethylferrocene (Me₂Fc) in the presence of metal ions (Mg²⁺ and Sc³⁺) exhibit the color change depending on temperature, accompanied by the concomitant change in the ESR signal intensity. In the case of Mg²⁺, electron transfer from Me₂Fc to PTQ is in equilibrium, when the concentration of the PTQ^•–– Mg²⁺ complex increases with increasing temperature because of the positive enthalpy for the electron-transfer equilibrium.

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p-Benzosemiquinone radical anion (Q^•–) forms 2:2 p-dimer radical anion complex [Q^•––(Sc³⁺)₂–Q] with Q and Sc³⁺ ions in deaerated MeCN. Addition of [R-(R, R)]-2,6-bis(4, 5-dihydro-4-phenyl-2-oxazolyl)pyridine [(R)-pybox] to Q-QH₂ system results in formation of the [Q^•––(Sc³⁺-(R)-pybox₂–Q] complex, which has strong absorption band at 583 nm, whereas the Q^•–) –(Sc³⁺)₂–Q complex has no absorption band at long wavelength region. The [Q^•––(Sc³⁺-(R)-pybox₂–Q] complex exhibits circular dichroism (CD) bands at long wavelength region.

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Rates of electron transfer from tris(2-phenylpyridine)iridium [Ir(ppy)₃] to 1-(p-Tolylsulfinyl)-2,5-benzoquinone (TolSQ) are accelerated by the presence of Sc³⁺. The observed pseudo-first-order rate constants (k_obs) obey high-order kinetics. Sc³⁺ promotes hydride transfer from 10-methyl-9,10-dihydroacridine (AcrH₂) to TolSQ. The k_obs value increases with increasing [Sc³⁺] to reach a limited value. When AcrH₂ is replaced by the 9,9'-dideuterated compound (AcrD₂), the rates of Sc³⁺-promoted hydride transfer decreased exhibiting a large primary kinetic isotope effect. The rates of hydride transfer from AcrD₂ to TolSQ are accelerated at high concentrations of Sc³⁺. This indicates that the Sc³⁺-catalyzed hydride transfer from AcrD₂ to TolSQ proceed via Sc³⁺-promoted electron transfer.

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Photoexcitation of a zinc phthalocyanine-perylenediimide (ZnPc-PDI) dyad affords the triplet excited state without the fluorescence emission, whereas addition of Mg²⁺ to the photoexcited ZnPc-PDI results in formation of a long-lived charge-separated state (ZnPc radical cation-PDI radical anion/Mg²⁺) in which PDI radical anion forms a complex with Mg²⁺. Similarly, Photoexcitation of a trinitrofluorenone-fulluren dyad (TNF-C₆₀) results in formation of long-lived charge separated state in the presence of scandium ion.

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Radical obtaining from biphenol and triphenol which hold phenyl substituent at ortho and para positions are more stable than that from 2,4,6-triphenylphenol. In order to elucidate a stabilization effct in the biphenol and triphenol radical species, the phenol oligomers bearing C₆H₅, 4-t-BuC₆H₄, 4-FC₆H₄ substituents at ortho and para positions were synthesized and their decomposition processes and thermal stabilities were examined.It was proved that the monomeric phenoxyl radical underwent hydrogen abstraction from the solvent to regenerate the starting phenol, while both demeric and trimeric phenoxyl radicals did intramolecular cyclization preferably to afford the corresponding dibenzofuran derivatives.

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Hydroquinone reacts with p-benzoquinone to form a charge transfer (CT) complex, so called, quinhydron. dimeric and trimeric benzoquinones and were synthesized, into which t-butyl and n-dodecyl substituents were introduced in order to enhance their solubility. In this paper, formation of quinhydrone-type complexes between oligomeric quinines and the corresponding hydroquinones was examined.
When quinine with t-butyl substituents was mixed with hydroquinone, neither in solution nor in solid were yielded quinhydron-type complex. This is probably due to sterically bulky t-butyl substituent (vide infra).
When quinine with n-dodecyl substituents was ground with hydroquinone in solid, the mixture immediately turn into deep purple.
Their different behavior should be ascribed to the bulkiness of their substituents. The spectral properties of the CT complexes will be reported in detail.

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Quinone derivatives occupy a significant position in orgarnic reaction, especially in an oxidation reaction. 2,3-Dichloro-5,6-dicyano-p-benzoquinone (DDQ) and 2,3,5,6-tetrachloro-p-benzoquinone (Chloranil) are well known as hydrogen abstraction reagents. DDQ has an advantage in reactivity higher than Chloranil, but it also possesses a disadvantage in terms of hydrogen cyanide generation on the way of hydrolysis process. Taking an advantageous property of Chloranil, we synthesized more powerful quinone derivatives composed of two or three Chloranil moieties, which would be expected to possess the high electron acceptability similar to DDQ. The fundamental properties such as reduction potentials and absorption spectra of the oligomeric Chloranil derivatives were examined. In this paper, the results will be reported in detail, together with those of their dehydrogenation ability.

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Biphenylene-substituted pentaarylruthenocenyl diphenylphosphine 1 was synthesized as a sterically hindered monophosphine ligand containing π-coordination moiety. The catalyst derived from 1 mol% of 1 and Pd(OAc)₂ was sufficient to effect the reaction of p-bromoacetophenone with phenylboronic acid in excellent yield even at room temperature in short reaction time.

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