12 - Formation of Carbon-Oxygen Bonds Via Organomagnesium Compounds

Abstract

This chapter explores the formation of carbon-oxygen bonds via organomagnesium compounds. The only effective methods for obtaining carbon-oxygen bonds from organomagnesium compounds involve reactions with compounds containing oxygen–oxygen bonds: dioxygen and peroxides. Reactions, which have been developed for organolithium compounds—with the molybdenum pentoxide-pyridine-hexametapol complex (“MoOPH”) and oxaziridines [E, G] are almost untried for organomagnesium compounds. Early investigations of reactions of Grignard reagents with oxygen gave only poor yields of the corresponding alcohols or phenols, and the reaction was generally regarded as a nuisance rather than as useful, though it aroused interest because of the observation of chemiluminescence. Indeed, the uncontrolled reaction tends to give mixtures of products, by complex reaction pathways. Yields of alcohols or phenols are better from organomagnesium compounds than from organolithium compounds (though organomagnesium iodides are liable to give iodo compounds as by-products). The alkylmetal compounds give better yields than arylmetal compounds, probably because the second stage of the reaction is faster. Thus, if an organolithium compound is initially available, it should be converted into the organomagnesium compound by treatment with magnesium bromide before oxidation, and yields of phenols may be improved by co-oxidation.