Coupling of Solvolysis and C?C Linkage: A Promising Synthetic Route to Functionalized Carboxylic Acids,Aldehydes, and Ketones

Numerous additions of carbocations to chloroolefins or acetylenes can be coupled with a solvolysis step when performed in a suitable acid; the products are variously substituted carboxylic acids, aldehydes, and ketones. Factors determining the success of these syntheses are the stability of the intermediate carbocations and suppression of the competing addition of protons to the unsaturated reaction component. Under the conditions of the Tscherniac-Einhorn reaction, amidomethylation of chloroolefins and acetylenes, i.e. the introduction of acylaminomethyl groups, is shown not to involve a trigonal α-chloro carbocation or a linear vinyl cation, but instead to proceed via a cyclic oxazinium ion intermediate.