Palladium-catalyzed reaction between aryl or alkenyl halides and (1-carbalkoxy-1-alkenyl)zinc iodides. A new class of unmasked β-substituted acrylate α-anion equivalents

Unmasked β-substituted acrylate α-anion equivalents have been directly and very efficiently prepared by insertion of zinc metal into the carbon-iodine bonds of alkyl (E)- or (Z)-2-iodo-2-alkenoates, (E)-or (Z)-(4), respectively. The stereoisomeric composition of these new reagents, 12, depends on the experimental conditions used for their preparation. Their Pd0-catalyzed reaction with alkenyl or aryl halides, which can contain functional groups, leads chemoselectively to the corresponding cross-coupled products in high yields. When the reagents 12 are synthesized from compounds (Z)-4 or long reaction times are used for their preparation, their cross-coupled products result are rich in the stereoisomers with trisubstituted double bonds of (E)-configuration.