Mechanistic alternatives in Lewis acid-catalyzed acyl halidealdehyde cyclocondensations

Abstract An investigation of the operative reaction mechanisms in Lewis acid-catalyzed acyl halidealdehyde cyclocondensations is presented. Aluminum-based catalysts promote cyclocondensation via a ketene-dependent reaction pathway while acyl halide enolates are implicated as reactive intermediates in Ti(IV)-catalyzed reactions.