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

Abstract

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).