3-Alkyl-1,2-cyclopentanediones by Negishi cross-coupling of a 3-bromo-1,2-cyclopentanedione silyl enol ether with alkylzinc reagents: an approach to 2-substituted carboxylic acid γ-lactones, homocitric and lycoperdic acids

Negishi cross-coupling of the silyl-protected 3-bromoenol of 1,2-cyclopentanedione with primary and secondary alkylzinc reagents using Pd-catalysts affords 3-alkyl substituted 1,2-cyclopentanediones in good yield. The method was applied to obtain 3-methylalkoxycarbonyl- and 3(2-Boc-aminoethyl)-alkoxycarbonyl-1,2-cyclopentanediones homocitric and lycoperdic acid precursors. Homocitric and lycoperdic acids were synthesized using asymmetric oxidation with the Ti(OiPr)(4)/tartaric ester/tBuOOH complex in two steps from the obtained precursors. (C) 2015 Elsevier Ltd. All rights reserved.