Roslan II, Ng KH, Chuah GK, Jaenicke S. Reagent-controlled regiodivergent intermolecular cyclization of 2-aminobenzothiazoles with β-ketoesters and β-ketoamides.
Beilstein J Org Chem 2017;
13:2739-2750. [PMID:
29564009 PMCID:
PMC5753174 DOI:
10.3762/bjoc.13.270]
[Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2017] [Accepted: 12/05/2017] [Indexed: 12/12/2022] Open
Abstract
Two regiodivergent approaches to intermolecular cyclization of 2-aminobenzothiazoles with β-ketoesters and amides have been developed, controlled by the reagents employed. With the Brønsted base KOt-Bu and CBrCl3 as radical initiator, benzo[d]imidazo[2,1-b]thiazoles are synthesized via attack at the α-carbon and keto carbon of the β-ketoester moiety. In contrast, switching to the Lewis acid catalyst, In(OTf)3, results in the regioselective nucleophilic attack at both carbonyl groups forming benzo[4,5]thiazolo[3,2-a]pyrimidin-4-ones instead.
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