Rearrangements of N-Acyl Isothioureas. Alternate Access to Acylguanidines from Cyanamides
摘要:
We report a tin-free one-pot radical approach to the synthesis of N-acyl isothioureas and acylguanidines from N-acyl cyanamides. Photoactivated reduction of aromatic disulfides in the presence of Hunig's base results in hydrothiolation of the cyanamide moiety, followed by spontaneous 1,3-migration of the acyl group. Onward reaction of the isothioureas obtained with amines led to the corresponding N-acylguanidines, where the acyl group is attached to the nitrogen atom formerly at the cyano-end of the starting material.
here a facile transamidation of N-cyano amides with various amines at ambient temperature without any additive. N-cyano amides preferred the trans conformation and have a reduced doublebond character revealed by crystal analysis. The DFT study indicates that the transamidation reaction proceeds through the direct attack of amine on the amide carbonyl since the LUMO (or LUMO+1) is located at the carbonyl