Yasuo Sekine

A carbon-carbon bond formation using endoperoxides of 1,2-dihydropyridines

Abstract A novel type of a nucleophilic substitution on the piperidine ring was achieved by a stannous chloride-effected reaction of endoperoxides of N-alkoxycarbonyl-1,2-dihydropyridines with various kinds of carbon nucleophiles.

Derivation of oxahomocubanes from dewar thiophene

Tetrakis-trifluormethyl-thiophen (I) liefert bei der Photolyse das Dewar-thiophen (II), das mit den Furanen (IIIa) und (IIIb) zu den Addukten (IV) reagiert, die zu (V) entschwefelt und dann zu den Oxa-homocubanen (VI) photolysiert werden.

Studies on organic fluorine compounds. Part 23. Diels–Alder reactions of 1,2,3,4-tetrakis(trifluoromethyl)-5-thiabicyclo[2.1.0]pent-2-ene

Diels–Alder reactions of Dewar thiophen (1) with acyclic and cyclic dienes have been examined. Butadiene gave the Diels–Alder adduct. Introduction of methyl groups at the 2- and/or the 3-position shortened the reaction time, and methyl groups on position 1 or 4 reduced the rate of the reaction. While cyclopentadiene and pyrrole reacted with compound (1) to give Diels–Alder adducts, substitution of the methylene group or at the nitrogen atom respectively, inhibited the reaction. From these results, the transition state of these Diels–Alder reactions is considered to be the exo-form. Cyclohexa-1,3-diene gave an adduct obtained by [4 + 2] reaction of the hexadiene and the thj-iran part of structure (1).

Synthetic studies on mitomycins. 2. A synthesis of 9a-hydroxy-5,8-dideoxomitosane skeleton through a novel retroaldol type of ring-opening reaction.

Abstract A synthesis of 9a-hydroxy-5,8-dideoxomitosanes was accomplished by the transannular cyclization of hydro-1-benzazocinone intermediates derived from 3-(2,5-dioxo-1-methylcyclopentyl)-6-methyl-p-phenylenediamine derivatives. These mitosanes were led to the 8-membered ring system by an oxidative ring-opening reaction.

Synthetic studies on mitomycins. 1. A regiospecific Michael addition of 2-methylcyclopentane-1,3-dione to p-toluquinonesulfonimides.

Abstract A Michael addition of 2-methylcyclopentane-1,3-dione to various p-toluquinone imides exclusively afforded the sole products in a regiospecific manner. Acid treatment of these adducts gave indole or benzofuran derivatives, which could be the key intermediates for synthesis of mitosane skeleton.