Silicon‐Mediated Coupling of Carbon Monoxide, Ammonia, and Primary Amines to Form Acetamides

Abstract

For the first time, a direct transformation of CO, NH3, and primary amines into acetamides, mediated by a main‐group element (silicon), is reported. Starting point is the selective deoxygenative reductive homocoupling of two CO molecules by the Fc‐bis(silylene) 1 a (Fc=ferrocendiyl) as a reducing agent, which forms the ferrocendiyl‐bridged disila(μ‐O)(μ‐CCO)ketene intermediate 2 a. Exposing 2 a to NH3 (1 bar, 298 K) and benzylamine yields the Fc‐disiloxanediamines [Fc(RHNSi‐O‐SiNHR)] 5 a (R=H) and 5 b (R=benzyl) under release of the respective acetamides H3CC(O)NHR, as confirmed by 13C‐isotope‐labelling experiments. IR and NMR studies of the reaction reveal a four‐step mechanism involving an N‐silylated carboxamide that can be isolated and fully characterized. The striking reaction mechanism for this unprecedented transformation involves a facile Si−C bond cleavage and ammonolysis of a Si−O bond, and has been demonstrated experimentally and by quantum‐chemical calculations.

A Striking Mode of Activation of Carbon Disulfide with a Cooperative Bis(silylene)

“…[6] Very recently,w er eported the isolation of ab is(NHSi)stabilized diphosphorus compound acting as P À transfer reagent and the cooperative activation of CO by the bis-(NHSis) A and B leading to disilaketenes such as C,w hich react with NH 3 or primary amines to afford acetamides. [7] For the latter,itturned out that cooperativity of the bis(NHSis) is key to bring about unprecedented activation modes of CO, resulting in ab is(NHSi)-m(CO) complex in the first step of activation. [8] Activation of CO 2 with mono-silylenes was intensively studied [9] and very recently,c ooperativity of bis(NHSis) towards activation of CO 2 could also be observed for A yielding ac yclic bis(silylated) carbonate.…”