New azasilatranes: sterically induced transannular bond weakening and cleavage

Abstract

Silylation of azasilatrane I (R = R1 = R2 = H) with ClSiMe3/NEt3 gives disilylated I (R = R1 = Me3Si, R2 = H) (II), via the spectroscopically detected monosilylated intermediate. Treatment of II with BuLi gives the stable lithiated deriv. I (R = R1 = Me3Si, R2 = Li) which can be converted to I [R = R1 = Me3Si, R2 = Me, Me3Si (III)], via reaction with MeI or ClSiMe3, resp. The novel structure of III, inferred from NMR data and confirmed by x-ray means, features an Nax nitrogen in a nearly trigonal pyramidal stereochem. with an exceptionally long NaxSi bond [ 2.775(7)?]. Reaction of III with MeOSO2CF3 gives IV, the Nax methylated product.