No abstract

The 13C and 3IP NMR data for stabilized and nonstabilized phosphorus-carbon ylides are compared to CNDO/2 and MINDO/3 molecular orbital calculations. Evidence of both an experimental and theoretical nature is presented that indicates that the carbon adjacent to phosphorus exists in a trigonal conformation. The molecular orbital calculations predict substantial ir interactions between the carbanion and phosphonium group. The various theoretical methods are compared to the trends in 13C and 31P chemical shifts developed for the compounds in this study. It is found that the negative charge in stabilized phosphoranes is delocalized over the framework of the molecules to a smaller extent than for analogous carbanions. The conformational preferences of ethylidene, cyclopropylidene, allylidene, and formylmethylenephosphorane are studied by theoretical techniques and the results are in agreement with available experimental data.

Treatment with base of N¢-aryl urea derivatives of hetero-or carbocyclic amines with benzylic nitrogen atoms promotes rearrangement with transfer of the aryl ring from N to C, giving rise to a-arylated products.

No abstract