One-pot organocatalytic domino Michael/alpha-alkylation reactions: direct catalytic enantioselective cyclopropanation and cyclopentanation reactions

Ibrahem, Ismail, Zhao, Gui-Ling, Rios, Ramon, Vesely, Jan, Sundén, Henrik, Dziedzic, Pawel and Córdova, Armando (2008) One-pot organocatalytic domino Michael/alpha-alkylation reactions: direct catalytic enantioselective cyclopropanation and cyclopentanation reactions. Chemistry - A European Journal, 14 (26), 7867-7879. (doi:10.1002/chem.200800442). (PMID:18618876)

Abstract

The development of one-pot organocatalytic domino Michael/alpha-alkylation reactions between bromomalonates or bromoacetoacetate esters and alpha,beta-unsaturated aldehydes is presented. The chiral-amine-catalyzed reactions with bromomalonates as substrates give access to the corresponding 2-formylcyclopropane derivatives in high yields with excellent diastereoselectivity and up to 99 % ee. The catalytic domino Michael/alpha-alkylation reactions between 4-bromo-acetoacetate and enals provide a route for the synthesis of functionalized cyclopentanones in good to high yields with 93-99 % ee. The products from the organocatalytic reactions were also reduced with high diastereoselectivity to the corresponding cyclopropanols and cyclopentanols, respectively. Moreover, one-pot combinations of amine and heterocyclic carbene catalysis (AHCC) enabled the highly enantioselective synthesis of beta-malonate esters (91-97 % ee) from the reaction between bromomalonates and enals. The tandem catalysis included the catalytic domino reaction followed by catalytic in situ chemoselective ring-opening of the 2-formylcyclopropane intermediates.

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Contributors

Author: Ramon Rios

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