Reactions of Ortho Esters Which Result in Carbon-Oxygen and Carbon-Halogen Bond Formation

Abstract

In this chapter are considered reactions of trialkyl orthocarboxylates and tetraalkyl orthocarbonates which result in the formation of new carbonoxygen or carbon-halogen bonds. In most of these reactions the ortho ester (or an alkoxycarbonium ion derived from it) functions as an alkylating agent.Many of these reactions are useful synthetic tools. These include formation and hydrolysis of cyclic ortho ester derivatives of diols and triols (which serve to protect the hydroxyl groups of the polyols, and provide means for their mild monoacylation), alkylation of phenols, enols and acids (to form ethers and esters), and conversion of carbonyl compounds to acetals and ketals. Other reactions, such as the alkylation of halogens by ortho esters, are of only limited synthetic utility, while still others, such as the acidcatalyzed hydrolyses of ortho esters, are of interest primarily because of the light they shed on the mechanisms of reactions of ortho esters with nucleophilic reagents.