Organozinc compounds inversion

SCHEME 1. The dynamic behavior of organozinc compounds involves C—Zn exchange and C—Zn bond inversion as main processes. Aggregation and ligand exchange dynamics complete the overall picmre describing the dynamics of these compounds... 

An interesting feature of the reaction of organozinc compounds is shown in Scheme 4. Reaction of /3-iodozinc derivative 1 with benzoyl chloride in the presence of Pd[P(o-tol)3l4 catalyst gave the iyn-isomer 2, while the anti-isomer 3 was produced by reaction of 1 with benzaldehyde followed by oxidation. The nucleophilic addition to the aldehyde occurs via inversion of the configurations in contrast to the Pd-catalyzed cross-coupling reaction, which proceeds via retention of the configurations. 

Bis(alk-2-enyl)zinc compounds 12, on addition to 3,3-dimethylcyclopropene, yield more than 90% of organozinc addition compounds 13 that can, by acidolysis, be converted into substituted cyclopropanes. Depending on the substitution pattern of the starting material, the reaction can be seen to proceed with allylic inversion. In contrast to addition reactions with unstrained double bonds, the reaction proceeds smoothly at — 20 to — 5 °C. Diethyl ether or tetrahy-drofuran can be employed as solvent and the cA-addition products are formed stereoselectively and in high yield. 

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