A NEW ORGANOPHOSPHORUS HETEROCYCLE

A new organophosphorus heterocyclic system, the 2,5-alkylidene-1,4-diphosphoniacyclohexane dihalide salts (2), was obtained by the tautomerization of the endocyclic diene isomers 1 in boiling glacial acetic acid, by the treatment of diphenyl-1-(alkyialkynyl)phosphine (3) with HX in glacial acetic acid, and by the cyclization of β-halovinylphosphine hydrohalides (4) obtained in the formation of 2. The relative stability of systems 1 and 2 and the mechanism of formation of these rings are discussed. Basic hydrolysis of system 2 leads, unexpectedly, to a monophosphine oxide. The mechanism of hydrolysis is also discussed. Proton nmr spectra (60 MHz) of the various examples of 1, 2, and 3 are also included. The 100-MHz nmr spectrum of one example of system 2 is reproduced in the paper. © 1969, American Chemical Society. All rights reserved.