Preparation of N-alkyl-N′-carboalkoxy guanidines: unexpected effective trans-alkoxylation transforming the 2,2,2-trichloroethoxycarbonyl into various carbamates

A range of N-alkyl-N′-Boc guanidines was simply synthezized from monoprotected Boc-1H-pyrazole-1-carboxamidine by reaction with primary amines. Synthesis of the hindered (R)-N-methylbenzyl-N′-Troc guanidine was achieved from the corresponding thiourea by the action of ammonia. Transformation of the Troc group into others carbamate groups, including Boc, was simply obtained by refluxing in the appropriate alcohol.