Pubblicato in Henry Rzepa's Blog

This is another of those textbook reactions, involving reaction of a carbonyl compound with a phosphonium ylid to form an alkene and a phosphine oxide. The reaction continues to be frequently used, in part because it can be highly stereospecific.  Thus the standard version tends to give Z -alkenes with good specificity, and is thought to proceed via an oxaphosphatane 4-ring intermediate.