Toshio Mukai

Photocycloreversion-reaction of a cage molecule and related cyclobutanes with cationic sensitizers

Abstract Irradiation of 1, 2, or 3 in acetonitrile in the presence of cationic sensitizer 7 or 8 afforded the cycloreversion product 4, 5 or 6, respectively. A wide range in quantum yields were found and these were dependent on the substrates and sensitizers.

Tetracyanoquinodimethanes Fused with 1,2,5-Thiadiazole and Pyrazine Units

1,2,5-Thiadiazolopyrazino-TCNQs underwent reversible four-stage one-electron reduction and gave conductive CT complexes with some donors. The X-ray structural analysis of the unsubstituted derivative revealed that the coplanar «sheet»-like network was formed by interatomic contacts of S--N≡C and H--N≡C in crystal

PHOTOCHEMICAL AND THERMAL REACTIONS OF SOME HETEROCYCLES CONTAINING C=N-O OR N=C-O GROUP

In connection with photochemistry of the non-constrained Ph-C=N-0 system, those of several 2-isoxazoline derivatives containing cyclobutene, cyclobutane, cyclopropane and cyclohexane rings, have been investigated as the models of the rigid and constrained Ph-C=N-0 system. In most cases, such 2-isoxazolines, upon irradiation, underwent the nitrogen-oxygen bond fission as the primary process, and produced a variety of products depending on the structures of the starting materials. For instance, the irradiation of 4-aryl-2-oxa-3-azabicyclo [3.2.0] hepta-3, 6-dienes afforded 2-aryl-1, 3-oxazepines, sometimes accompanied by pyrrole aldehydes, whereas 2-isoxazolines fused with small ring yielded B-aminoaldehydes, oxazolines, azirine aldehydes, and small fragments such as benzonitrile. The photochemical reaction mechanisms of several 2-isoxazolines have been studied using low-temperature technique. In addition, the pyrolytic reactions of 4-phenyl-2-oxa-3-azabicyclo [3.2.0] heptadiene and 1, 3-oxazepines as well as their valence isomers have been examined to compare with their photochemical behavior. It was found that in pyrolysis of bicyclo [3.2.0] heptadiene derivatives containing the C=N-O or N=C-O group, the cyclobutene ring fission occurs prior to the nitrogen-oxygen or carbon-oxygen bond cleavage. Reaction mechanisms for the deep-seated rearrangements of the 1, 3-oxazepines and of 2-oxa-3-azabicyclo [3.2.0] hepta-3, 6-dienes to pyrrole aldehydes were discussed. The results indicate the major differences in the chemical behaviors of the photolytically and thermally excited states for those heterocycles.

Semiconductor-catalyzed photocycloreversion, valence isomerization and [1,3]-sigmatropic rearrangement

Abstract The semiconductor-catalyzed photochemical [2+2]cycloreversion of n-methylquinolone dimer, valence isomerization of hexamethyl(Dewar)benzene, and [1,3]-sigmatropic rearrangement of 2,2-bis(4-methoxyphenyl)-1-dideuteriomethylenecyclopropane gave N-methylquinolone, hexamethylbenzene, and 2,2-bis(4- methoxyphenyl)-3,3-dideuterio-1-methylenecyclopropane, respectively.

Photochemistry of 3-aryl-2-isoxazoline1

Abstract 3-Phenyl-2-isoxazoline (1) was irradiated to give 4-phenyl-2-oxazoline (3), β-aminoaldehyde (14) and benzonitrile from its π-π* singlet excited state. Several related derivatives afforded similar photoproducts on irradiation. The quantum yields of the photoreactions were dependent on the magnitudes of the singlet energies of the 2-isoxazolines. p-Cyanophenyl-2-isoxazoline (1c) formed a one-to-one photoadduct (22) with benzene.

A new reaction of nitrene with 1H-azepine derivatives: a formation of 2,6-diazabicyclo[3.3.0]octadiene and 2,8-diazabicyclo[3.2.1]octadiene☆

Abstract The formation of two diazabicyclooctadienes ( 2 and 3 ) is elucidated by the intermediacy of azahomoazepine.

Electrochemical studies of fused-pyrrole systems

Abstract An electrochemical study of fused pyrroles, i.e. , 1,4-dihydropyrrolo-[3,2-b]pyrrole (PP), 3,6-di-t-butyl-1,4-dihydropyrrolo[3,2-b]pyrrole (BPP) and dimethyl 1,4-dihydro-3,6-di-t-butyl-pyrrolo[3,2-b]pyrrole-1,4-dicarboxylate (BMPP), was carried out. PP could be polymerized electrochemically on InSn oxide conducting glass (ITO), basal-plane pyrolytic graphite, Pt or Au electrodes, while BPP and BMPP could not be electropolymerized. The polymeric film (PPP) prepared from PP was electroactive in both acetonitrile and aqueous solutions. The morphology of PPP films was found to depend on the supporting electrolytes used. The conductivity of the film was 5 × 10 −5 S cm −1 just after its preparation and decreased gradually when exposed to air. The film thickness (φ) was linearly related to the amount ( Q ) of charge passed in the polymerization, with Q in the range 5 to 150 mC cm −2 (slope of the φ versus Q plot: 4 μm C −1 cm 2 ). The PPP film was found to undergo degradation via electrochemical oxidation at the electrode and chemical oxidation by oxygen in air. Furthermore, the physical and electrochemical properties are compared with those of polypyrroles, polymers of other fused heterocycles, etc.

Synthesis and physical properties of 6,12-diarylazuleno[1,2-b]azulenes

Abstract The structure of a minor dimer ( 2a ) of 1-arylcycloheptatrienylidenethylene was determined by X-ray crystallography. Dehydration of 2a and 2b gave novel non-benzenoid aromatics---6,12-diarylazuleno[1,2-b]azulenes ( 3a and 3b ), whose electronic and NMR spectral properties were reported.

Photocycloaddition reactions of tricyclo[3.3.1.02,8]nona-3,6-dien-9-one (barbaralone) and carbonyl compounds

Abstract Barbaralone undergoes two types of cycloadditions with photoexcited p-chloranil, p-bromanil, and p-fluoranil at the C 1 -C 3 and C 4 -C 6 positions through a locally excited triplet exciplex and an ion radical pair, respectively.

Divergent rearrangement pathways in the electron-transfer induced spiropentane-methylenecyclobutane rearrangement: Role of cip and ssip

Abstract Photogenerated 1,1-diarylspiropentane cation radicals competitively rearranged to the more thermodynamically stable 1-(diarylmethylene)cyclobutanes and the less stable 2,2-diaryl-1-methylenecyclobutanes in a concerted and stepwise manner, respectively.