NOVEL SILICON AND PHOSPHORUS-CONTAINING HETEROCYCLES

The reactions of two or three equivalents of lithium phosphinomethanid es with di- or trifunctional chlorosilanes yield novel five- and six-m embered heterocycles with silicon and phosphorus ring members by multi step rearrangements and/or transmetallation reactions. Silaethene inte rmediates are likely to be involved. Three different types of reaction s are described. (1) RSiCl(3)(a, R = Ph; b, R = Me; c, R = (1)Bu) reac ts with three equivalents of Li[C(PMe(2))(2)(SiMe(3))] to give five-me mbered heterocycles (R)[(Me(3)Si)C(PMe(2))(2)]Si-C(SiMe(3)) = PMe(2)-P Me-CH2, 11, which are fluxional in solution. A PMe(2) group shift and transmetallation reaction are involved in their formation. (2) PhSiCl( 3) reacts with {Li[C(PMe(2))(SiMe(3))(2)]}(2) x TMEDA to give a five-m embered heterocycle (Ph)(Me)Si-C(SiMe(3))(2)-SiMe(2)-PMe(2) = C(SiMe(3 )), 17, via an intermediate mono- and disubstitution product. This rea ction involves ligand rearrangement, elimination of Me(2)PCl, and an, Me(3)Si and Me group shift within a silaethene framework. (3) Ph(2)SiC l(2) reacts with two equivalents of Li[CH(PMe(2))(2)] to give a six-me mbered heterocycle [Ph(2)Si-C(PMe(2)) = PMe(2)-](2), 18, by transmetal lation and LiCl elimination, possibly via a silaethene intermediate. X -ray analyses of 11a, 17 and 18 confirm the proposed molecular structu res based on nuclear magnetic resonance spectroscopy.