Phosphonyl transfer by the elimination-addition mechanism: accelerated formation of an alkylidineoxophosphorane (phosphene) intermediate when a P-O single bond is replaced by P-S.
The phosphonochloridate R(2)CHP(O)(YEt)Cl (R(2)CH = fluoren-9-yl, Y = O or S) reacts with Pr(i)(2)NH largely or exclusively by an elimination-addition mechanism; the three-coordinate phosphene intermediate R(2)C=P(O)YEt is formed ca. 10(3) times more easily when Y = S than when Y = O.
Harger
Martin J P
MJ
Department of Chemistry, University of Leicester, Leicester, UK LE1 7RH. mjph2@le.ac.uk