A Novel One-pot Synthesis Of Vicinal Diamines With Benzaldehyde And Aniline Derivatives Mediated By BiCl₃/Zn

One of the most convenient routes to vicinal diamines is through the reductive coupling of imines. A variety of catalysts and reductants have been developed for this purpose. Metals and Lewis acids have been widely used as reductant and catalyst for the coupling of imines. To date, imines, the starting materials, have to be prepared beforehand. Only some simple imines are commercial available, but the prices are still high. Although the reaction to generate imines is simple, the purification is still tedious and lead to the loss of products. This problem limits the application of the coupling reaction of imines. This paper developed the synthesis of vicinal diamines with benzaldehyde and aniline derivatives. The procedure is an efficient and economical method which avoids the step of the purification of imines.The main research results listed as follows:1. The optimal reaction conditions for synthesis of vicinal diamines in one pot: Bi Cl3(10%) was added in an untreated solvent of ethanol, stir to dissolved, aldehyde(1.0 equiv), primary amine(1.1 equiv), Zn powder(3.0 equiv) were added to react under reflux temperature for 5h. vicinal diamines was obtained in high yield.2. In this paper, 28 compounds were prepared. Among them, 10 compounds were yielded in more than 85%, 9 compounds were given in yields of 70~85%, the remained compounds were obtained in yields of 30~60%. Specifically, the reaction afforded 7 new compounds. Steric and electronic effects on the reaction have been also investigated. The paper indicated the ortho groups have effect on the configuration of vicinal diamines.