REACTIONS OF PHOSPHINE MONOIODOBORANES WITH 4,4'-DI-TERT-BUTYLBIPHENYLIDE AND ELECTROPHILES - TRIAL OF GENERATION OF TRICOORDINATE BORON ANIONS AND SYNTHESIS OF B-FUNCTIONALIZED PHOSPHINE BORANES

The generation and reactions of tricoordinate boron anions have been investigated using phosphine-boranes. Tricyclohexylphosphine-monoiodoborane was reduced by 2 equiv of lithium 4,4'-di-tert-butylbiphenylide (LDBB) in tetrahydrofuran at -78 degrees C. The generated chemical species reacted with a variety of electrophiles such as water, chlorotrimethylsilane, diphenyl disulfide, methyl trifluoromethanesulfonate, ethylene bride, benzaldehyde, diethyl carbonate, and carbon dioxide to afford phosphine-boranes possessing a substituent at the boron atom. Reaction of tri-tert-butylphosphine-monoiodoborane with LDBB, followed by treatment with water or benzyl bromide, provided di-tert-butylphosphine-borane or benzyl(di-tert-butyl)phosphine-borane, respectively. These transformations are reasonably interpreted by assuming the existence of tricoordinate boron anions as reactive intermediates.