Substituent-Controlled Reactions of Tminophosphoranes with Methyllithium

摘要

Phosphorus ylides R_3P=CR_2 and phosphine oxides R_3P=O can react with nucleophiles via hypervalent intermediates. These intermediates might be regarded as electronically similar to the valence-expanded [PX_4]~ ions. The Wittig reaction, in which an intermediately formed oxaphosphetane resulting from the reaction of a phosphorus ylide and a carbonyl compound decomposes to give phosphine oxide and the related olefin, has been well studied. Another example of the above-mentioned reactions is that of apyridyl-substituted phosphine oxide with organometallic bases. Aryl- and heteroaryl-substituted tertiary phosphanes can react to give either substituent-exchange (Scheme 1, top) or substituent-coupling products (Scheme 1. bottom).