Rhodium-Catalyzed Regioselective Synthesis of Isocoumarins through Benzothiadiazine-Fused Frameworks

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• 作者：Prashant B. Dalvi ; Kuang-Ling Lin ; Manohar V. Kulkarni ; Chung-Ming Sun
• 刊名：Organic Letters
• 出版年：2016
• 出版时间：August 5, 2016
• 年：2016
• 卷：18
• 期：15
• 页码：3706-3709
• 全文大小：372K
• 年卷期：0
• ISSN：1523-7052

文摘

An unprecedented two-step, one-pot synthesis of benzimidazothiadiazine 5,5-dioxides is presented. Reaction condition based regioselectivity has been achieved where fused benzimidazo[1,2-b][1,2,4]thiadiazines are exclusively formed under thermal conditions, whereas benzimidazo[2,1-c][1,2,4]thiadiazines were created only under microwave irradiation. The salient features of this protocol include a regioselective sulfonylation of 2-aminobenzimidazole with o-halo sulfonyl chlorides followed by N–C bond formation. The acid forms of these fused regioisomers have been used to introduce novel guanidine-containing isocoumarin frameworks.