摘要:
                                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.  The first involved the reaction of trialkyltin azides with 4'-methyl-1,1'-biphenyl-2-carbonitrile (3).  The resultant trimethyltin-tetrazole adduct could be hydrolyzed with acid to yield biphenylytetrazole 6.  The tri-n-butyltin-tetrazole adduct, however, was transformed into the corresponding N-trityl-protected tetrazole 5 to permit removal of the organic soluble tri-n-butyltin byproducts.  The trityl group also permits 5 to be brominated at the benzylic position and then alkylated by imidazole derivatives.  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 10 using N2O4 (g) to yield N-(2-cyanoethyl)-protected tetrazole 12.  Aqueous base removes the cyanoethyl protecting group to yield biphenylyltetrazole 6.  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.