A STABLE SPIROCYCLIC TETRAOXA(HYDRO)-PHOSPHORANE CONTAINING A SIX-MEMBERED RING

Abstract

Abstract The tetraoxa(hydro) spirophosphorane, 3 containing a six and five-membered ring is isolated in 66% yield from the reaction of 2-chloro-1,3,2-dioxaphosphorinane, 1 and triethylammonium perfluoropinacolate, 2. Hexaflouroacetone inserts into the P[sbnd]H bond of 3 to form the pentaoxaphosphorane, 6 which is obtained in a different way from phosphite, 5 and hexafluoroacetone. 2-Methoxy-1,3,2-dioxaphosphorinane, 7 and hexafluoroacetone furnish spirophosphorane, 8, the methoxy derivative of 3. 1H and 19F NMR spectra of the phosphoranes show rapid pseudorotation processes equilibrating substituent positions in the trigonal bipyramidal geometry at phosphorus. The 1H NMR data of the six-membered ring are in accord with a time averaged conformation of a flattened chair.