A convenient method for the preparation of 1,2-diamines

A convenient method for the preparation of 1,2-diamines was developed by Michael addition of an amino group equivalent to nitro olefins, followed by the reduction of the obtained adducts to the corresponding 1,2-diamines. After screening various amino group equivalents, it was found that O-alkylhydroxylamines were quite effective to produce 1,2-diamines in high yields, while ammonia and benzylamine gave unsatisfactory results. These two reactions, addition and reduction, could be carried out simply in one-pot reaction; that is, Michael addition of O-alkylhydroxylamine to nitro olefins rapidly proceeded just by treating nitro olefins with O-alkylhydroxylamine hydrochloride and sodium hydrogencarbonate in tetrahydrofuran. After the addition reaction was completed, a palladium catalyst and ethanol were directly added to the reaction mixture. The resulting mixture was then stirred under an atmospheric pressure of hydrogen at room temperature to yield the desired 1,2-diamines. The above convenient one-pot procedure for the preparation of 1,2-diamines was successfully applied to various nitro olefins. Palladium on activated carbon was a suitable catalyst for the hydrogenation of the adducts to afford the corresponding 1,2-diamines in 77-88% yields. The adducts formed from aliphatic nitro olefins and O-alkylhydroxylamine were converted to the desired 1,2-diamines in 87-92% yields by using palladium hydroxide on activated carbon.