Asymmetric induction in the nucleophilic cyclopropane ring cleavage reaction with vitamin B12s

Article abstract of DOI:10.1021/om00153a025

Vitamin B_12s reacts with cyclopropane derivatives having electron-withdrawing substituents such as acetyl, methoxycarbonyl, and cyano groups to give 3-substituted propyl-cobalt complexes. The alkylation with prochiral 1-acetyl-1-alkylcyclopropanes results in an asymmetric induction (ee 24-33%) at carbon 3 in the resulting alkyl ligands. Examination of the ¹H NMR spectra of the alkylation products indicates that (1) two prochiral methyl groups in 3,3-diacetylpropyl- and 3,3-bis(methoxycarbonyl)propyl-cobalt complexes are rendered diastereotopic by the presence of the chiral B₁₂ and are observed to be spectroscopically nonequivalent and (2) enantiomeric methyl groups in 3-acetyl-3-alkylpropyl- and 3-acetyl-3-(methoxy-carbonyl)propyl-cobalt complexes having an asymmetric center at carbon 3 are also rendered diastereotopic and spectroscopically distinguishable in a similar manner.