Revisiting the 7-Phospanorbornene Family: New P-Alkyl Derivatives

A series of 1-alkyl-3-methyl-2,5-dihydro-1H-phosphole oxides were converted to the corresponding phosphole oxides that, by the Diels-Alder reaction with N-maleimide derivatives or with another unit of phosphole oxide, yielded trapped phosphole oxides or phosphole oxide dimers, respectively, as new 7-phosphanorbornene 7-oxides. The stereostructures of three derivatives were evaluated by single crystal X-ray analysis. The regio- and stereospecific dimerization was studied by B3LYP/6-31G(d,p) quantum chemical calculations, whose results were in accord with syntheses. Novel mechanistic features were explored. The geometrical data obtained by single crystal X-ray analysis validated the results of quantum chemical calculations, as the deviation was less than 3%. (C) 2015 Wiley Periodicals, Inc.