Studies of the reactions of 3H-pyrrolizines with acetylenes

Johnson, David

Abstract

An attempt was made to synthesise azonia-azulenium salts by the 2+2 cycloaddition of acetylenes to 3H-pyrrolizine, and the subsequent ring expansion of the cyclobutene product.
In Part I the attempted syntheses of some new 3Hpyrrolizines are described and a review is included on the syntheses of 3H-pyrrolizines already known.
Part II describes the reactions of 3H-pyrrolizines with dimethyl acetylenedicarboxylate and includes a brief review on the reactions of dimethyl acetylenedicarboxylate with compounds closely related to 3H-pyrrolizine. The thermal reactions of 3H,1-methyl-3H and 1,2-dimethyl-3Hpyrrolizines, with dimethyl acetylenedicarboxylate, gave derivatives of 3-carbomethoxy (carbomethoxymethyl) methylene- 3H-pyrrolizine and cycl [4,2,2] azine. Attempts to prepare the cycl [4,2,2] azini um sys tem from a cycl [4,2,2] azine derivative are described, and a review is included on the synthesis and properties of known cyclazines.
The photochemical reaction of dimethyl acetylenedicarboxylate with 3H-pyrrolizine gave a low yield of cyclobutene derivatives and a larger yield of the thermal products. The photochemical reaction with 3,3-dimethyl-3H-pyrrolizine, however, gave a moderate yield of the cyclobutene derivative.
The cyclobutene ring of this photolysis product was successfully opened to give a pyrrolo [1,2-a] azepine.

Citation

Johnson, D. (1972). Studies of the reactions of 3H-pyrrolizines with acetylenes