Liquid‐phase CO‐oxidation of aldehydes and olefins radical versus non‐radical epoxidation

Abstract

In co-oxidations of aldehydes and olefins with molecular oxygen in the liquid phase, epoxides are formed via two different routes: (1) by reaction of intermediate acylperoxy radicals with the olefin, and (2) by a non-radical reaction of intermediate peracid with the olefin. For the systems benzaldehyde cis-l,2-D,-1 -octene and benzaldehyde cis-and trans-2-octene the ratio of radical to non-radical epoxidation has been calculated with the aid of the kinetic relationships derived for this type of reaction and has been determined experimentally from the stereo selectivity of the expoxidation and from the production of carbon dioxide. The results show that the ratio of radical to non-radical epoxidation increases with increasing reactivity of the olefm as well with increasing olefin/ aldehyde ratio.

Mechanistic Studies on the Mukaiyama Epoxidation

“…Mechanism of Aerobic Limonene Epoxidation with Co-Oxidation of an Aldehyde. The mechanism of alkene epoxidation by aerobic co-oxidation with an aldehyde was thoroughly investigated in the early seventies (see, for example, Vreugdenhil and Reit and Tsuchiya and Ikawa) and has been reviewed by Sheldon and Kochi . For the uncatalyzed reaction, Lassila et al have envisaged both a radical and a nonradical pathway.…”

Optimizing the Synthetic Potential of O2: Implications of Overpotential in Homogeneous Aerobic Oxidation Catalysis

“…A peracid can also form under the reaction conditions and mediate epoxidation of the alkene substrate (Prilezhaev reaction) . Other studies show that epoxidation in the absence of a metal cocatalyst can take place via parallel acylperoxyl radical and peracid-mediated epoxidation pathways. − Conditions can be biased to promote the peracid-mediated epoxidation pathway (e.g., by using excess aldehyde), benefiting from the coarctate transition state to retain the olefin stereochemistry in the epoxide (Figure B). , Mukaiyama epoxidation reactions are prototypical chemical examples of monooxygenase reactivity, wherein reductive activation of oxidant of O 2 generates a higher-potential oxidant capable of promoting a thermodynamically challenging oxidation reaction.…”