Tetrazolo piperazines

Another application was shown with -amino alcohols being converted into fused tri- and tetrazolo-piperazines by Gouty et al. [210] with high dia-stereoselectivity and regioselectivity depending on the substitution pattern of the starting material (Scheme 62). 

The alcohol 303 is converted into a chloride 304 which can be replaced afterward by an azide group. Intramolecular cychzation gives tetrazolo-piperazines 305. The cycloaddition is carried out in DMSO under heating... 

Scheme 62 Synthesis of fused tetrazolo-piperazines 306 using readily available starting materials. Those structures can be further functionalized diastereoselectively by using anionic chemistry [210]...

These compounds have been referred to as tetrazolo[l,5-c]pyrazines, and reduced derivatives have been named tetrazolo[l,5-a]piperazines. This ring system has attracted attention mainly in the study of tetrazolo azide tautomerism and has been used to generate nitrenopyrazine. Although tetrazolo derivatives of pyridazine and pyridine are stable in solution, tetrazolo[l,5-a]pyrazine isomerizes readily in chloroform or trifluoracetic acid. Although an earlier report indicated that no azide... 

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