Synthesis of Variously 2-Substituted Alkyl (Z)- and (E)-2-Alkenoates and (Z)- and (E)-α-Ylidene-γ-butyrolactones via Palladium-Mediated Cross-Coupling Reactions between Organostannanes and Organic Halides

Article abstract of DOI:10.1016/S0040-4020(01)89314-5

Stereoisomerically pure trisubstituted α,β-unsaturated ester of general formula 7 have been efficiently synthetized using two different protocols.The first one involves the palladium(0)/copper(I)-mediated cross-coupling reaction between alkyl (E)-2-tributylstannyl-2-alkenoates, (E)-2, and aryl or alkenyl iodides.The second protocol, which allows to prepare stereodefined 2-aryl, 2-methyl, 2-(1-alkenyl) as well as 2-acyl substituted α,β-unsaturated esters, is based on the cross-coupling reaction between easily available alkyl (Z)- or (E)-2-halo-2-alkenoates and organostannanes in NMP, in the presence of catalytic amounts of PdCl2(PhCN)2, AsPh3 and CuI. (Z)- and (E)-2-ethenyl substituted α,β-unsaturated esters prepared according to this procedure have been proven to be useful precursors to (Z)- and (E)-α-ylidene-γ-butyrolactones, (Z)- and (E)-8, respectively.