Yoshikazu Sugihara

Thienoborepins: Conjugation characteristics in boron heterocycles

Abstract Protonolysis, complex-formation with amines, ab initio molecular orbital calculations with 3-21G basis set, redox potentials, and spectroscopic features of 1-phenylthieno[3,4-d]borepin (1) and 1-phenylthieno[2,3-d]borepin (2) were examined. The compound 1 was shown to be more labile than 2, which give us a guide for construction of stable heteroaromatics. Absorption and fluorescence spectra of 1 and 2 revealed the potential ability of boron heterocycles in the field of the organic optical materials.

The reactions of 4,5-dehydrotropone with 4-phenyloxazols

Abstract 4,5-Dehydrotropone reacted with 4-phenyl-, 5-methyl-4-phenyl-, and 2,5-dimethyl-4-phenyloxazol to give, involving facile loss of benzonitrile from the corresponding Diels-Alder adducts, furo-[3,4-d]tropone and its 1-methyl and 1,3-dimethyl derivative, respectively. Protonation of furo[3,4-d]-tropones yielded delocalized 6-hydroxy-3-oxaazulenium ions.

Acid-catalyzed ethanolysis of di-l-azulenyl ketones

Abstract Substituted di-l-azulenyl ketones composed of 3,8-dimethtyl-5-isopropyl-l-azulenyl and/or 4,6,8-trimethyl-l-azulenyl group were refluxed in ethanol in the presence of p -toluenesulfonic acid to give substituted azulenes and ethyl azulene-l-carboxylates derived from the cleavage of either of C-CO bonds of di-l-azulenyl ketones. The facility and the product distributions of the ethanolysis were affected markedly by the substituents.

4-Acetoxytricyclo[4.1.0.02,7]Hept-4-en-3-one; synthesis and novel bond reorganization of a valence isomer of 2-acetoxytropone

4-Acetoxytricyclo[4.1.0.02,7]hept-4-en-3-one (3), a valence isomer of 2-acetoxytropone, was synthesized. Upon heating in pyridine at 150°C, 3 rearranged into 1-acetoxybicyclo[3.2.0]hepta-3,6-dien-2-one (9); the mechanism of which was examined by means of deuterium labeling experiments.

Acid-catalyzed rearrangement of 2-substituted and 2,4-disubstituted 8H-3-oxaheptalen-8-ones to 1-acyl-6-hydroxyazulenes

Abstract It was found that intrifluroacetic acid, 2-methyl 8H-3-oxaheptalen-8-one was transformed into 2-hydroxy-3-methyl-7H-benzocyclohepten-7-one and 1-formyl-6-hydoxy-2-methylazulene, whereas 2,4-dimethyl-8H-3-oxaheptalen-8-one was under the same conditions into 1-acetyl-2-methyl-6-hydroxyazulene. 2-Phenyl- and 2,4-diphenyl-8H-3-oxaheptalen-8-on undergo the same skeletal as those which corresponding mono- and dimethyl derivatives suffer from, respectively.

Synthesis and properties of a bridged phenalenone incorported into bicyclo[3.2.2]nonane skeleton. 6,9-dihydro-6,9-ethenocyclohepta[gh]phenalen-1-one

6,9-Dihydro-6,9-ethenocyclohepta[gh]phenalen-1-one (1) has been synthesised starting from the Diels-Alder adduct (6) of acepleiadiene (5) and maleic anhydride through 10 steps with reasonable yields. Spectroscopic properties of 1 suggestged the intramolecular electron supply from the remote ethylenes to the phenalenone π-systems in the ground-state of this molecule.

Some Preparation Methods of a Tricyclo[4.1.0.02,7]Hept-4-En-3-One Skeleton

Abstract β-Elimination of acetic acid was elaborated in our synthetic method of a tricyclo[4.1.0.02,7]hept-4-en-3-one (tropovalene) skeleton. Presented was a new synthetic method of this skeleton, which consists of a reaction sequence of 1,4-addition of propanethiol to bicyclo[3.2.0]hepta-3,6-dien-2-one, photochemical construction of bicyclobutane skeleton, oxidation, and thermal elimination of sulfenic acid.