73086-47-2Relevant academic research and scientific papers
Reactions with Diazoazoles. Part VI. Unequivocal Synthesis of 3-Methyl-3H-azolotetrazoles. Correction of the Formerly Described 3-Methylazolotetrazoles in Favour of Mesoionic 2-Methylazotetrazoles
Ege, Guenter,Heck, Reinhard,Gilbert, Karlheinz,Irngartinger, Hermann,Huber-Patz, Ursula,Rodewald, Hans
, p. 1629 - 1639 (2007/10/02)
3-Methyl-3H-pyrazolotetrazoles 2 and 3-methyl-6-phenyl-3H-1,2,4-triazolotetrazole (4) have been unequivocally synthesized by annelation of the tetrazole moiety to the pyrazole resp. 1,2,4-triazole system.The constitution of some N-methyl substituted azolotetrazoles, formerly described as 3-methyl-3H-pyrazolotetrazoles 2, 3-methyl-6-phenyl-3H-1,2,4-triazolotetrazole (4) and 1-methyl-6-phenyl-1H-1,2,4-triazolotetrazole (5), has to be revised in favour of the corresponding mesoionic 2-methyl derivatives 2', 4', 5'.The structures of 3-methyl-3H- as well as of 2-methyl-2H-pyrazolotetrazole derivatives 2a, 2c, 2'a have been determined by X-ray analyses.The azapentalenic system is aromatic in all three measured compounds and mesoionic in the case of the 2-methyl-2H-substitution pattern.The phenyl and ester substituents are coplanar with the azapentalene system. 3-, 2-, and 1-Methylpyrazolotetrazoles exhibit different behaviour when allowed to react wit stannous chloride or sodium ethoxide.Azolotetrazoles with a methyl substituent at N-1, N-2 or N-3 of the tetrazole moiety can be distinguished by a combination of 1H and 13C nmr with respect to the chemical shifts of the N-methyl group and the bridgehead carbon.Results of semiempirical calculations of the pyrazolotetrazole anion and of its N-methyl derivatives are discussed.
