Preparation of 2‐Amino‐1,3‐butadienes as N‐Pyridine Derivatives

Abstract

2‐Amino‐1,3‐butadienes as pyridine derivatives have been prepared from corresponding dihydrothiazolo[3,2‐a]pyridinium salts in reactions with a strong base. The pyridinium salts were prepared from pyridine‐2(1H)‐thiones and trans‐1,4‐dibromo‐2‐butene by a vicinal and chemoselective formation of 3‐vinyldihydrothiazolo[3,2‐a]pyridinium salts. A strong base was used for selective proton removal from the vinyl‐substituted 3‐position. A subsequent ring opening provided 2‐substituted 1,3‐butadienes with the azine appended at the annular nitrogen. Simple S‐alkylation yielded a corresponding azinium salt, thereby introducing electrophilic character to the 1,3‐butadiene system. Hydrolysis of the sulfide function provided the corresponding pyridin-2(1H)‐one attached to the 1,3‐butadiene in the 2‐position.