Metal- and Catalyst-Free, Formal [4 + 1] Annulation via Tandem C═O/C═S Functionalization: One-Pot Access to 3,5-Disubstituted/Annulated Isothiazoles

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• 作者：Gaurav Shukla ; Abhijeet Srivastava ; Maya Shankar Singh
• 刊名：Organic Letters
• 出版年：2016
• 出版时间：May 20, 2016
• 年：2016
• 卷：18
• 期：10
• 页码：2451-2454
• 全文大小：389K
• 年卷期：0
• ISSN：1523-7052

文摘

An operationally simple and user-friendly new protocol for the synthesis of 3,5-disubstituted/annulated isothiazoles is devised utilizing β-ketodithioesters/β-ketothioamides and NH₄OAc via C═O/C═S bond functionalization under metal- and catalyst-free conditions. The strategic [4 + 1] annulation initiated by NH₄OAc is carbon-economic and relies on a sequential imine formation/cyclization/aerial oxidation cascade forming consecutive C–N and S–N bonds in one pot. A wide range of previously inaccessible and synthetically challenging isothiazoles are compatible with this transformation under nontoxic conditions with excellent functional group tolerance. The products bear useful synthetic handles for further functionalization.