Hidefumi Kato

Novel rearrangement of twisted 2,4-di-alkyl 2-trans-4-trans pentadienals: An approach to cyclopentenones based on molecular mechanical consideration

Rearrangement of 2,4-di-trans-pentadienals IVa-d was described as a consequence of the successive alkyl substitutions on the C-2 and C-4 positions. 1H-FT nmr spectroscopy suggested that the reaction involves ketene VIII as an intermediate.

Bridging effects of furan ring incorporated in the perimeters of a bisdehydro[16]annulene and a bisdehydro[18]annulene: syntheses of 1:14-epoxy-6,8-bisdehydro[16]annulene and 1:16,10:13-diepoxy-4,6-bisdehydro[18]annulene

Aus Furan-2,5- dialdehyd (I) erhalt man mit dem Phosphoniumsalz (II) den homologen Dialdehyd (III), der mit weiterem Phosphoniumsalz (IV) zum Di-acetylen (V) fuhrt.

Preparation of oxygen-bridged aza[15]- and aza[17]annulene dicarboxylates by intramolecular azide cyclization

Abstract Aza[15]annulene dicarboxylate ( 12 ), aza[15]annulenone dicarboxylate ( 13 ) and aza[17]annulene dicarboxylate ( 19 ) were prepared. Compound ( 12 ) proved to be paratropic, and ( 19 ) proved to be diatropic.

Chemical transformations of 4:7,10:13-diepoxy[15]annulenone by carbonyl transposition reactions

Abstract The titled annulenone 1 could be converted into new annulenones 3 and 8 by carbonyl transposition reactions. Compound 8 can be regarded as the first 14π hydroxy-enone as a higher homolog of tropolone (6π) and hydroxy[11]annulenones (10π), and was proved to be aromatic.

A simple methodology for aza-annulene synthesis: preparation and propreties of 2,15-diethoxycarbonyl-4,7:10,13-diepoxy-2-cis,8-cis, 14-cis-aza[15]annulene

The synthesis and properties of the titled compound (9) are described; (9) was prepared by the thermolysis of the vinyl azide (5) in 70% yield, and no furopyrrole derivatives were formed.

Synthesis of a bridged homo[15]annulenium ion

Aus dem Annulenon (I) erhalt man mit Dimethylsulfoniummethylid das Homoannulenon (II), das durch Decarboxylierung und Reduktion mit Boranat in das Diol (III) ubergefuhrt wird.

The synthesis of an oxygen-bridged hydroxy[15]annulenone: The effects of introducing one hydroxy group into the flexible segment of a 14π perimeter

Mono-trans-hydroxy[15]annulenone (6) forms a keto-enol tautomeric mixture with the keto tautomer (7) in CH2Cl2; (6) was rapidly isomerized into the cis-enol (8) on dissolution in dimethylformamide, dimethyl sulphoxide, and MeOH, indicating that the intramolecular H-bond of (6) is easily broken owing to the motional freedom of the segment on which the OH group was introduced.

The three dimensional structure of all-cis-diepoxy[15]annulenone and some implications from the structure

An X-ray structural analysis of all-cis-diepoxy[15]annulenone (1) revealed that (1) exists in two different conformations, each of which possesses a saucer-like three-dimensional geometry, like that of the polyaromatic 14π hydrocarbon corannulene (5).

4:7,10:13-Diepoxy-1-aza[16]annulene and 3:6,9:12,15:18-triepoxy-2-chloro-1- aza-[18]annulene as the first examples of oxygen-bridged aza-[4n]- and -[4n + 2]annulenes

The title compounds were prepared by the Beckmann rearrangement of diepoxy[15]- and triepoxy[17]-annulenone oximes (2) and (11), respectively; 4:7,10:13-diepoxy-1-aza[16]annulene (5) exists as two tautomers, the keto form (5a) and the dipolar form (5b), forming a paratropic 16π system; 3:6,9:12,15:18-triepoxy-2-chloro-1-aza-[18]annulene (12) proved to be strongly diatropic (18π).