Mechanism of the Reaction of Amines with 5-[(Aryl- or Alkylamino)hydroxymethylene]-2,2-dimethyl-1,3-dioxane-4,6-diones in the Presence of Chlorotrimethylsilane (Me3SiCl)

Addition of chlorotrimethylsilane (Me3SiCl) to the mixture of a carbamoyl-substituted Meldrum's acid, i.e., a 5-[(arylamino)hydroxymethylene]-2,2-dimethyl-1,3-dioxane-4,6-dione of type 1 and a secondary amine as nucleophile strongly accelerated the rate of their reaction. The reason for this phenomenon observed, during our previous research, remained, however, unclear. To elucidate the mechanism of this reaction, we assumed and verified three possible pathways for the action of Me3SiCl (cf. Scheme2): The acceleration of the reaction is caused i) by formation of a O-trimethylsilylated Meldrum's acid of type 2, ii) by the silylated amine 3, or iii) by the presence of HCl liberated from Me3SiCl. The performed experiments revealed that the faster course of reaction is caused by the formation of N-trimethylsilylated amines of type 3.