Chemically induced dynamic nuclear polarization in the dehalogenation of gem-dihalocyclopropanes under the action of i-Bu2AlH in the presence of Zr(acac)4

Abstract

The integral and multiplet effects associated with the chemically induced dynamic nuclear polarization in the catalytic dehalogenation of alkyl-and aryl-gem-dibromocyclopropanes under the action of diisobutylaluminum hydride in the presence of Zr(acac)4 have been discovered and investigated. The main products of the reaction are monobromocyclopropanes and cyclopropanes. The other reaction products are isobutane, isobutylene, and isobutyl bromide. Integral polarization is observed for the isobutylene protons; multiplet polarization, for the isobutyl bromide protons. Integral polarization arises in a geminal singlet radical pair between an isobutyl radical and a Zr(III) paramagnetic ion that have resulted from the homolysis of an i-Bu-Zr bond.