Acetylene-allene-1, 3-diene rearrangement of C4-unsaturated sulfides

Abstract

1. The isomerization of 1-tert-butylthiobutadiene-2,3 by the action of alkali at 130–132° in alcoholic medium leads to the formation of a complex mixture of compounds, containing various aliene, acetylene, and 1,3-diene sulfides. The main isomerization products are 1-tert-butylthiobutadiene-1,3 and 1-tert-butylthiobutyne-1, whose multiple bonds are conjugated with the heteroatom. 2. Under analogous conditions 1-tert-butylthiobutyne-1, 1-tert-butylthiobutyne-2, and also 1-tert-butylthiobutadiene-1, 2 form an equilibrium mixture which does not contain compounds with a 1,3-diene structure. 1-tert-Butylthiobutyne-1 is the main component of this mixture, in which the sulfur atom is conjugated with the C=C bond. 3. The rearrangement mechanism is considered as a prototropic process, proceeding through the formation (by the action of alkali) of intermediate mesomeric anions. Consideration is also given to the role of the heteroatom in this isomerization.