Base-Mediated Synthesis of Imidazole-Fused 1,4-Benzoxazepines via 7-exo-dig Cyclizations: Propargyl Group Transformation.

Date

2025-04-04

Author

Korkmaz Cokol, Nalan
İnyurt, Fevzi Can
Öktem, İpek
ŞAHİN, Ertan
Sari, Ozlem
Dengiz, Çağatay
Balci, Metin

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Herein, we describe the synthesis of a series of imidazole-fused 1,4-benzoxazepines using 7-exo-dig cyclizations. Two sets of substrates, one containing disubstituted alkyne functional groups and the other featuring terminal alkynes, were synthesized by using O-propargylation, Sonogashira cross-coupling, and condensation reactions between aldehydes and o-diaminobenzene. While the disubstituted substrates yielded exocyclic E/Z configured cyclization products smoothly, the reactions involving terminal alkynes resulted in the formation of isomeric products with altered skeletal structures, in addition to the expected 7-exo-dig cyclization products. Density functional theory (DFT) calculations were used to clarify the mechanisms underlying the formation of these products. It is suggested that these unexpected products are formed through a series of intermolecular O-to-N-propargyl transfer reactions, followed by 7-exo-dig cyclization, in accordance with Baldwin’s rules. Furthermore, this study extensively demonstrates the conversion of exocyclic products to endocyclic products through a base-mediated 1,3-H shift.

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https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=105001118571&origin=inward
https://hdl.handle.net/11511/114366

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Department of Chemistry, Article