Aza-annulation of enaminones with crotonyl chloride - formal reversal of regioselectivity

Article abstract of DOI:10.1016/S0040-4020(97)00755-2

The regiochemistry of aza-annulation of enaminones with a,β-unsaturated acid chlorides bearing hydrogen atoms on the γ-carbon is reversed when triethylamine is used as mediator. When the reaction was carried out at lower temperatures a 3-acyl β,γ-unsaturated compound could be isolated which cyclised to the desired product under thermal or basic conditions. The nature of this intermediate strongly suggests that a vinyl ketene is the active acylating agent.