Roslan Irwan Iskandar, Ng Kian-Hong, Chuah Gaik-Khuan, Jaenicke Stephan
Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543.
Beilstein J Org Chem. 2017 Dec 18;13:2739-2750. doi: 10.3762/bjoc.13.270. eCollection 2017.
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 KOBu and CBrCl as radical initiator, benzo[]imidazo[2,1-]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), results in the regioselective nucleophilic attack at both carbonyl groups forming benzo[4,5]thiazolo[3,2-]pyrimidin-4-ones instead.
已经开发出两种区域发散方法，用于2-氨基苯并噻唑与β-酮酯和酰胺的分子间环化反应，反应受所用试剂控制。以布朗斯特碱叔丁醇钾和四氯化碳作为自由基引发剂，通过进攻β-酮酯部分的α-碳和酮羰基来合成苯并[]咪唑并[2,1-]噻唑。相反，改用路易斯酸催化剂三氟甲磺酸铟，会导致在两个羰基上发生区域选择性亲核进攻，生成苯并[4,5]噻唑并[3,2-]嘧啶-4-酮。
