Rhodium Catalazed Enantioselective [4+1] Cycloaddition Of Diazoarylacetates And The Danishefsky Diene

Highly functionalized and optically enriched cyclopentenone are ubiquitous structural motif in many natural products and act as important intermediate in organic synthesis.Much efforts have been devoted the rapid and efficient access to the synthetically important molecules.Compared to the well explored [3+2]cycloaddition,enantioselective [4+1] cycloaddition of metal carbene and electron enriched diene is less studied.We have previously developed an enantioselective formal [4+1] cycloaddition of 3-diazo indolin-2-one and Danishefsky diene.However,when the diazo compound was switched to acyclic aryl ?-diazoacetate,no enantioselectivity was observed.Herein we described a rhodium-diene catalyzed enantioselective formal [4+1] cycloaddition of aryl ?-diazoacetate and Danishefsky diene.The corresponding cyclopentenone with an all carbon stereo center was thus achieved in up to 96% yield and with up to 92% ee.The reaction proceeded a first[2+1] cycloaddition followed a further rearrangement of the formed vinyl cyclopropane.This methodology was successfully applied in the total synthesis of(-)-1,13-Herbertenediol in total yield of 34% featured optically active cyclopentenone as the key intermediate using 2-hydroxyl-5-methyl-1-phenyl methyl ketone as the starting material.