New phosphabenzenes by [4 + 2] cycloaddition of stannoles to 1-phospha-1-alkynes — determination of signs of coupling constants
摘要:
Stannoles bearing dialkylboryl groups in 3-position react with 1-phospha-1-alkynes P=C-(t)Bu (1) and P=C-CH(2)(t)Bu (2) by [4 + 2] cycloaddition and elimination of stannylene to give phosphabenzenes in high yield. The stannylenes oligomerise to give [R(2)(1)Sn](n) with n greater than or equal to 7 (R = Me, Et, -(CH2)(5)- or, in the case of R(1) = (t)Bu, react with the stannole itself. All phosphabenzenes are characterised by their consistent sets of NMR data. The absolute signs of the coupling constants (n)J(P-31, H-1), (n)J(P-31, C-13), (2)J(P-31, Si-29) and (2)J(Sn-119, P-31) were determined by appropriate 1D and 2D NMR experiments.