ASYMMETRIC APPROACHES TO CYCLOPENTENONES IN THE NI(0)-PROMOTED CYCLOCARBONYLATION REACTION OF ALLYL HALIDES AND ACETYLENES

Different approaches to the asymmetric synthesis of cyclopentenones by means of the Ni(CO)(4)-promoted alkyne-allyl halide cyclization-carbo nylation are reported. The use of acetylenic sulfoxides 1 has proved e ffective for the synthesis of acyclic, fused [5+8], and spiro [5+5], [ 5+7], and [5+8] cyclopentenones, whereas placement of the aryl sulfoxi de on the allylic system failed to afford any cycloadduct. Homochiral fused [5+8], and spiro [5+7] and [5+8] cyclopentenones have been obtai ned by this methodology. Finally, a modest enantioselectivity was obse rved when different homochiral alpha-substituted carboxylates were use d as ligands in our reaction system. Copyright (C) 1996 Elsevier Scien ce Ltd