Three synthetic routes to a sterically hindered tetrazole. A new one-step mild conversion of an amide into a tetrazole

TLDR: In this article, a tetrazole synthesis with a sterically hindered o-tetrazole group was described. But the synthesis was performed by three different routes, one of them employing a new tetrazoles synthesis.

Abstract: 5-[4'-Methyl-1,1'-biphenyl-2-yl]-1H-tetrazole (6), which contains a sterically hindered o-tetrazole group, was synthesized by three different routes, one of them employing a new tetrazole synthesis. Subsequent acid hydrolysis of the trityl protecting group of 5 yielded biphenylyltetrazole 6. The second synthesis involved the nitrosation of an N-(2-cyanoethyl)-protected biphenylamidrazone. The third method involves the novel transformation of an N-(2-cyanoethyl)-substituted amide into the corresponding N-(2-cyanoethyl)-protected tetrazole in one step using triphenylphosphine, diethyl azodicarboxylate (DEAD), and azidotrimethylsilane. Subsequent base hydrolysis of the cyanoethyl group yielded 6 as before. Examples are also provided of the application of this new reaction to other N-(2-cyanoethyl)-protected carboxamides