THE McMURRY COUPLING AND RELATED REACTIONS

摘要

Reductive coupling of carbonyl compounds leading to pinacols or alkenes is a powerful synthetic transformation. The deoxygenative coupling of carbonyl compounds leading to the formation of alkenes is a rather newly developed synthetic method relative to other transformations such as the classical pinacol coupling. In 1970 Schreibmann first reported the formation of alkenes as minor products in the pinacol coupling of aromatic carbonyl compounds with aluminum amalgam.1 The reductive coupling of both aromatic and aliphatic aldehydes and ketones using low-valent tungsten species generated by treatment of WCl6 with two equivalents of BuLi was described shortly thereafter.2 Although the process remains inefficient for the preparation of aliphatic alkenes, it works well to provide various stilbenes. The seminal deoxygenative carbonyl coupling with highly oxophilic titanium species was reported independently in 1973 and 1974 by Mukaiyama,3 Tyrlik,4 and McMurry.5 The TiCl3-LiAlH4 system developed by McMurry was the first synthetically useful transformation of aliphatic carbonyl compounds into alkenes, demonstrating the versatility of the coupling system.