Theoretical Analysis of the Stereoselectivity in the Ozonolysis of Olefins. Evidence for a Modified Criegee Mechanism

Abstract

The Criegee mechanism of the ozonolysis of cis and trans symmetric alkenes of the type RCH=CHR is investigated by semiempirical AM1 calculations. The observed stereoselectivity trends are qualitatively explained in terms of the original Criegee mechanism. However, it is shown that in order to elucidate some subtle stereochemical effects as well as to account for the vain attempts to detect the carbonyloxide intermediate, a modification is required. This is done by adopting a proposal made by Cremer et al. (Chem. Phys. Lett. 1991, 187, 491) for the specific case of ethylene and applying it to all systems. The carbonyl oxide and aldehyde formed upon dissociation of the primary ozonide are not separated but form a strongly bound complex that subsequently transforms to the secondary ozonide.