Amination of bis(trimethylsilyl)-1,2-bisketene to ketenyl amides, succinamides, and polyamides: Preparative and kinetic studies

The reaction of the bisketene (Me3SiC=C=O)(2) (1) with amines is facile and proceeds by two distinct steps forming first ketenylcarboxamides 3 and then succinamides 5. Successive reaction of 1 with two different amines gives mixed succinamides, while phenylhydrazine gives succinimide 7. The reactions of 1.8 equiv of 1 with 1,4-(H2NCH2)(2)C6H4 gives alpha,omega-bisketenyldiamide 13, while equivalent amounts of 1 and diamines gave polymeric amides. Mixed ester amides 8 are formed by sequential reaction of 1 with an alcohol, followed by an amine, or vice versa. Kinetic studies of the amination reaction of 1 with excess amines in CH3CN gave rate constants k(obs) for the formation of ketenylcarboxamides that were fit by the relationship k(obs) = k(a)[amine](2) + k(b)[amine](3). Further reaction of the n-butyl ketenylcarboxamide 3b with n-BuNH2 to give the succinamide 5b was first order in [n-BuNH2], while the further reaction of the CF3CH2 ketenylcarboxyamide 3c with CF3CH2NH2 to form 5c was fit by the equation k(obs) = k(c)[amine](2)/(k(d)[amine] + 1). The reaction of 3b with CH3OH to form the ester amide 8a is strongly accelerated compared to CH3OH addition to the corresponding ketenyl ester and gives significant stereoselectivity for formation of erythro product, and both these effects, as well as the absence of higher order kinetic terms in the reaction of 3b with n-BuNH2 may arise from coordination by the carboxamido group to the nucleophile.