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Stereoselective Synthesis of Highly Functionalized Cyclopropanes. Application to the Asymmetric Synthesis of
Philippe Dorizon1, Guifa Su, Gitte Ludvig
1Laboratoire des Carbocycles (Associé au CNRS), Institut de Chimie Moléculaire d'Orsay, Bât. 420, Université de Paris-Sud, 91405 Orsay, France.
Abstract:
One-pot palladium(0)-catalyzed alkylation and S(N)(') cyclization of 1,4-dichlorobut-2-ene 1 by the anion of alpha-substituted carbonitriles 2a-d can provide highly functionalized cyclopropanes (E)-4a-d, diastereoselectivity, (de 88-100%). Several attempts to achieve the asymmetric synthesis of the 1-amino-2-ethenylcyclopropanecarbonitrile (E)-9, by means of this new procedure, i.e., using chiral palladium ligands, chiral aminoacetonitriles (-)- and (+)-12 (from 1-hydroxypinanone) or chiral allyl chlorides (4S)-20b-d and (4R)-20e (from (2S) ethyl lactate) have pointed up the reversibility of the palladium-catalyzed cyclization step, responsible for the low enantioselectivity observed (ee 88%) and provided the enantiomerically enriched 1-amino-2-propenylcyclopropanecarbonitrile (E)-22 (ee > 83%) suitable precursor of (1S,2S)-2,3-methanoamino acids.