Reactivity of B←P coordinated phosphide with isocyanides: Bases or nucleophiles?

Abstract

The reactivity of the sodium phosphido-borane complex, [Na(THF)₃]+[1-BCy₂-8-PPh-C₁₀H₆]– (1), with RCH2NC isocyanides is reported. In contrast to traditional bases or phosphides, 1 act as an efficient nucleophile to form reactive carbanion intermediates instead of proton abstraction from RCH2NC and formation of protonated phoshane 1-BCy2-8-P(H)Ph-C10H6 (2). This study showed that 1 acts as a nucleophile and reacts with RCH2NC in a 1:2 stoichiometry to form a 2-imidazoline, imidazole or an enamine. Isolated compounds demonstrate the ability of 1 in promoting carbanion formation and participating in subsequent reactions to give various N-substituted alkyl phosphine organic compounds, which are not usually obtained by different synthetical approaches.