Syntheses and mechanistic investigations of formamides, formamidines, and formimidates

Formamide, formamidine, and formimidate compounds are the organic compounds that have been used in the synthesis of pharmaceutically active compounds and in various industries. This work presents convenient and efficient methods for preparing 3 kinds of products: formamidine, formimidate, and formamide from an amine and triethyl orthoformate (TEOF) under different reaction conditions. Aniline was chosen as a model compound. Various experimental parameters were varied including type of solvent, mole ratio, reaction time, and reaction temperature. It was found that to obtain formamidine, using ethanol as a solvent and 1 equivalent of TEOF at 60 °C in 2 h produced the desired product at 91% yield. The highly efficient protocol for formimidate was carried out under solvent-free condition using 5 equivalents of TEOF at 60 °C and the formimidate product was obtained at 98% yield within 24 h. To produce formamide, 24 equivalents of TEOF in deionized water at 70 °C were used to achieve 97% yield in 24 h. These methods are highly favorable because they are catalyst-free, low-cost, easy, and fast and provide excellent yields.