Synthesis of 9-nitro-5H-spiro[benzo[b]tetrazolo[1,5-d][1,4]oxazepine-4,2′-oxirane] via an unusual ring-expansion

• Published in: Tetrahedron letters Vol. 59; no. 47; pp. 4158 - 4160
• Main Authors: Kolluri, Rao, Zhang, Jing, Singh, Rajinder, Duncton, Matthew A.J.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 21-11-2018
• Subjects: Benzo[1,5-d][1,4]oxazepine; Epoxide (oxirane); Heterocycle; Oxetane; Ring-expansion; Spirocycle; Ring-expansion; Spirocycle; Benzo[1,5-d][1,4]oxazepine; Heterocycle; Epoxide (oxirane); Oxetane
• ISSN: 0040-4039; 1873-3581
• DOI: 10.1016/j.tetlet.2018.10.016

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•An unusual ring-expansion to prepare 9-nitro-5H-spiro[benzo[b]tetrazolo[1,5-d][1,4]oxazepine-4,2′-oxirane].•A medium-ring and spirocyclic epoxide (oxirane) are formed in the reaction.•The spirocyclic epoxide (oxirane) could be reacted further.•Compounds are useful for medicinal chemists.
Attempted cyclization of (4-(hydroxymethyl)-8-nitro-4H-benzo[b]tetrazolo[1,5-d][1,4]oxazin-4-yl)methyl 4-methylbenzenesulfonate 2 did not give the expected spirooxetane product 1, but instead provided 9-nitro-5H-spiro[benzo[b]tetrazolo[1,5-d][1,4]oxazepine-4,2′-oxirane] 3via an unusual ring-expansion process. The structure of compound 3 was confirmed by single-crystal X-ray crystallography. The spiroepoxide (oxirane) in compound 3 could be ring-opened with a variety of nucleophiles to give products of potential interest to medicinal chemists.