Asymmetric approaches to cyclopentenones in the Ni(0)-promoted cyclocarbonylation reaction of allyl halides and acetylenes

Abstract

Different approaches to the asymmetric synthesis of cyclopentenones by means of the Ni(CO) 4-promoted alkyne-allyl halide cyclization-carbonylation are reported. The use of acetylenic sulfoxides 1 has proved effective for the synthesis of acyclic, fused [5+8], and spiro [5+5], [5+7], and [5+8] cyclopentenones, whereas placement of the aryl sulfoxide on the allylic system failed to afford any cycloadduct. Homochiral fused [5+8], and spiro [5+7] and [5+8] cyclopentenones have been obtained by this methodology. Finally, a modest enantioselectivity was observed when different homochiral α-substituted carboxylates were used as ligands in our reaction system.