An Improved Synthesis of Valsartan

Biphenyltetrazole group, an important component of sartans, is usually formed in excellent yield by the reaction of 4'-alkylbiphenyl-2-carbonitrile with excessive organotin azide. However, it is restricted in industrial scale because of the difficult post-treatment. In this article, an improved synthetic method for valsartan and the quantitative recovery of tri-n-butyltin chloride are reported. During this process, the tetrazole-Sn complex and excessive organotin azide were decomposed by HCl to furnish tri-n-butyltin chloride, and then reacted with NaF to lead to filterable polymer tributyltin fluoride which was converted again to tributyltin chloride by HCl in ethyl acetate. This approach is facile for the efficient manufacture of sartans using organotin azide to form the tetrazole group and is valuable for industry readers.