Some reactions of phosphorus ylids.

Both the methods of preparation, and the reactions, of phosphorus ylids are reviewed. The reactions of activated triple bonds with phosphorus ylids are studied and shown to give rearranged products, probably via a four-membered cyclic transition state. A brief outline of the mechanism of the Wittig reaction is given, and reactionsof intermediate betaines in the Wittig reaction, other than olefin formation, are studied. The reaction of phosphines with epoxides is used to demonstrate betaine dissociation and rearrangement. Following a review of abnormal quaternisation reactions of activated alkyl halides, the reaction of triphenylphosphine with 1-bromo-nitroalkanes, to give a-hydroxyimino- alkyl phosphonium salts, is discussed. A brief review of the reactions of aldehydes and ketones with trivalent phosphorus compounds is followed by a more detailed study of the reaction of aminophosphines with aldehydes and ketones to give rearranged products.