FeCl3-Catalyzed Formal [3+2] Cyclodimerization of 4-Carbonyl-1,2-diaza-1,3-dienes

Abstract

Substituted 1-aminopyrroles are easily accessible by iron-catalyzed cascade reaction of 1,2-diaza-1,3-dienes. Mechanistically, a formal [3+2] cyclodimerization is hypothesized to proceed through a [4+2] cyclodimerization of 4-substitued 1,2-diaza-1,3-dienes followed by intramolecular ring closure to fused diaziridin-pyrrolines which is successively opened to undergo a ring contraction process and consequently generate the desired pyrrole moiety. The presence of activated hydrogen in the terminal position of the azo-enic moiety is crucial for the synthesis of pyrroles.