Latent Carbene: Diaminomethylation of Thiophenes

The reaction of silylformamidine with various halo- and ethoxycarbonyl substituted thiophenes was studied. It proceeded via C-H bond insertion of the nucleophilic diaminocarbene that exists in an equilibrium with silylformamidine affording aminals. The reaction proceeded more readily at the 2(5)-position compared to the 3(4) one. The number of halogens at the thiophenes markedly influences the reaction. The more halogens, the higher the reaction rate. Even one electron acceptor group at the thiophene ring is enough to promote the reaction. As a rule, the reaction does not require solvents or catalysts. Hydrolyses of the aminals provides a novel convenient approach to substituted thiophene aldehydes.

Automated summary

The reaction of silylformamidine with various halo- and ethoxycarbonyl substituted thiophenes was studied. It proceeded via C-H bond insertion of the nucleophilic diaminocarbene that exists in an equilibrium with silylformamidine affording aminals. The reaction proceeded more readily at the 2(5)-position compared to the 3(4) one. The number of halogens at the thiophenes markedly influences the reaction. The more halogens, the higher the reaction rate. Even one electron acceptor group at the thiophene ring is enough to promote the reaction. As a rule, the reaction does not require solvents or catalysts. Hydrolyses of the aminals provides a novel convenient approach to substituted thiophene aldehydes.