78848-71-2Relevant articles and documents
Praeparative und NMR-spektroskopische Beitraege zum Isomerieproblem der Carbodiphosphorane
Schmidbaur, Hubert,Deschler, Ullrich
, p. 2491 - 2500 (2007/10/02)
The substituent effect on the carbodiphosphorane/methylenephosphorane isomerism (AB) has been investigated.In contrast to Me(Ph)2P=C=P(Ph)2Me (1A), the benzyl analogues 2B, 3B do not exist as carbodiphosphoranes, but as conjugated double-ylides Me(Ph)2P=CH-P(Ph)2=CHPh and PhCH2(Ph)2P=CH-P(Ph)2=CHPh, respectively.However, an equilibrium mixture of cumulated and conjugated double-ylides (4A, 4B and 5A, 5B) is observed in the corresponding mesitylmethyl compounds.Like the benzyl group, the fluorenyl substituent causes an exclusive existence of the conjugated double-ylide Flu(Ph)2P=CH-P(Ph)2=Flu (7), while the corresponding mono-ylides (Ph)2P-CH=P(Ph)2-CHPh (11B') and (Ph)2P-CH2-P(Ph)2=Flu (6) differ in the position of their ylide function.The 2-pyridinylmethyl compound appears as a mixture of isomers (Ph)2P-CH=P(Ph)2-CH2Pyr (10B') and (Ph)2P-CH2-P(Ph)2=CHPyr (10A').These relations are easily explained on the basis of a carbanion stabilization through the substituent resonance. - Phosphane and phosphonium salt precursors, derivatives, and by-products have been characterized.
