Synthesis and reactions of β-enamino phosphonium salts. Preparation of 2-vinyl-1-aza-1,3-dienes and penta-l,4-dien-3-ones

Abstract

Reaction of N,P,P,P-tetraphenyl-λ⁵-phosphazene 1 and prop-2-ynyltriphenylphosphonium bromide 2 followed by addition of aliphatic, heteroaromatic and aromatic aldehydes leads to β-enamino phosphonium salts 7, while substituted tetrahydropyridines 9 are obtained when α,β-unsaturated aldehydes are used. Functionalized phosphonium salts 7 are precursors of Wittig reagents and act as intermediates in the synthesis of 2-vinyl-1-aza-1,3-dienes 11 and penta-l,4-dien-3-ones 12.