Heterocycles from Phosphonium-Iodonium Ylides. Photochemical Synthesis of λ5-Phosphinolines

A photochemical reaction of mixed phosphonium-iodonium ylides with acetylenes yielding lambda(5)-phosphinolines, a rare class of phosphorus heterocycles hardly accessible by other methods, was found. The yields of lambda(5)-phosphinolines vary from 35% to 80%. The structures of two phosphinolines were established by single-crystal X-ray diffraction. The X-ray diffraction and NMR spectra data indicate the superposition of ylidic and aromatic structures for phosphinolines.