jo901559d_si_007.cif (11.98 kB)

Asymmetric Synthesis of All-Carbon Benzylic Quaternary Stereocenters via Conjugate Addition to Alkylidene and Indenylidene Meldrum’s Acids

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posted on 20.11.2009, 00:00 by Ashraf Wilsily, Eric Fillion
A systematic study outlining the enantioselective 1,4-addition of dialkylzinc reagents to 5-(1-arylalkylidene) and indenylidene Meldrum’s acids is presented. Variation of the aryl and alkyl groups present on the alkylidene was thoroughly explored. The 1,4-addition displayed compatibility with a wide range of heteroaromatics and functional groups, and the arene pattern of substitution affected enantioselection, with a para-substituted aryl group consistently leading to high enantioselectivities. The nature of the organozinc reagent on the efficiency and selectivity of the conjugate addition was also investigated. The solid-state conformation was determined for a number of alkylidene Meldrum’s acids and correlated with the observed enantioselectivity in relation to the arene pattern of substitution.