Facile synthesis of macrocyclic tetrazoles by regioselective cycloalkylation of bistetrazoles with 2,5-dimethylhexane-2,5-diol in perchloric acid

Alkylation of 1,5-bis(tetrazol-5-yl)-3-oxapentane with 2,5-dimethylhexane-2,5-diol in 65% aqueous perchloric acid was found to proceed selectively on the N2 atoms of both tetrazole rings generating a 15-membered macrocycle with tetrazol-2,5-diyl moieties incorporated (yield ca. 80%). Under analogous alkylation conditions 1,5-bis(1-methyltetrazol-5-yl)-3-oxapentane undergoes quaternization resulting in a macrocyclic tetrazolium perchlorate containing two 1-methyltetrazolium-3,5-diyl units linked by 3-oxapentane-1,5-diyl and 2,5-dimethylhexane-2,5-diyl bridges. Crystal structures of the macrocyclic compounds obtained, determined by single crystal X-ray analysis, are described.