Synthesis of functional Δ3-1,3,5-oxazaphospholene and 2H-1,4,2-diazaphosphole complexes via catalytic ring expansion reactions of a 2H-azaphosphirene complex

Catalytically-induced ring expansion of 2H-azaphosphirene complex using ferrocenium hexafluorophosphate and acetone (), diethylketone (), cyclohexanone (), benzaldehyde () or para-hydroxy-benzaldehyde () furnished selectively the Δ3-1,3,5-oxazaphospholene complexes , whereas with ortho- and para-hydroxy- or ortho- and para-amino-substituted benzonitriles the 2H-1,4,2-diazaphosphole complexes were obtained. Two further findings are noteworthy: (1) The significant decreased reaction time in the case of the sterically more demanding carbonyl derivatives and (2) the formation of diastereomers in the case of and with a ratio of 8:1 and 9:1, respectively. All products were characterized by NMR, MS and elemental analysis and the configuration of complexes and were determined by X-ray single-crystal diffraction analysis.