Veltri L, Amuso R, Petrilli M, Cuocci C, Chiacchio MA, Vitale P, Gabriele B. A Zinc-Mediated Deprotective Annulation Approach to New Polycyclic Heterocycles.
Molecules 2021;
26:molecules26082318. [PMID:
33923572 PMCID:
PMC8072660 DOI:
10.3390/molecules26082318]
[Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Revised: 04/12/2021] [Accepted: 04/15/2021] [Indexed: 11/25/2022] Open
Abstract
A straightforward approach to new polycyclic heterocycles, 1H-benzo[4,5]imidazo[1,2-c][1,3]oxazin-1-ones, is presented. It is based on the ZnCl2-promoted deprotective 6-endo-dig heterocyclization of N-Boc-2-alkynylbenzimidazoles under mild conditions (CH2Cl2, 40 °C for 3 h). The zinc center plays a dual role, as it promotes Boc deprotection (with formation of the tert-butyl carbocation, which can be trapped by substrates bearing a nucleophilic group) and activates the triple bond toward intramolecular nucleophilic attack by the carbamate group. The structure of representative products has been confirmed by X-ray diffraction analysis.
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