1,3,2-DIAZAPHOSPHININES AND -DIAZAARSININES AS PRECURSORS FOR POLYFUNCTIONAL PHOSPHININES AND ARSININES

Thermal reactions of 4,6-di-tert-butyl-1,3,2-diazaphosphinine 1a, obtained from the reaction of the corresponding diazatitanacycle with PCl3 in the presence of NEt3, with various functional alkynes are dicussed. Phosphinines are produced in good yields (from 55 to 75%) via two [4 + 2] cycloaddition−cycloreversion sequences with extrusion of two molecules of pivalonitrile from 1a. Two 2-diethoxymethyl-substituted, 3 and 4, one 3-propynyl-substituted, 6, and two examples of 3-monosubstituted and 3,5-disubstituted ferrocenylphosphinines, 8 and 9, have been synthesized. The X-ray structure of the 2,6-bis(trimethylsilyl)-3,5-bis(ferrocenyl)phosphinine 9 has been determined. Due to a strong steric crowding between the silyl and ferrocenyl groups, the ring adopts a twisted geometry with a dihedral angle of 11.65°. Upon reaction of 1a with bis(diphenylphosphino)acetylene, a 2,3-bis(diphenylphosphino)-substituted, 11, and the 2,3,5,6-tetrakis(diphenylphosphino)-substituted, 12, phosphinines have been obtained. Rea...