Der Mechanismus der Umlagerung substituierter Aminoacrylderivate

Abstract

Thioacetic acid and dithioacetic acid react with push-pull- acetylenes of the type (CH₃)₂N—C=C—CO-R (1) in the same way as other carboxylic acids: The addition to dimethylaminopropinal (1a) at low temperatures yields, after rearrangement of the very instable primary adducts, Z-3-acetoxy-N,N-di- methyl-thioacrylamide (5) and Z-3-thioacetoxy-N,N-dimethyl- thioacrylamide (7) respectively. The structure of the two compounds can be proved by spectroscopic evidence of (5) and (8), which are formed by elimination of thioketene from (7). According to the distribution of S-atoms in (5) and (7), two reaction pathways including 4-membered rings can be ruled out. Thus the rearrangement of 3-acyloxy-N, N-dimethylacrylamides most probably proceeds by a mechanism including a dipolar six-membered intermediate.