Hazra G, Maity S, Bhowmick S, Ghorai P. Organocatalytic, enantioselective synthesis of benzoxaboroles
via Wittig/oxa-Michael reaction Cascade of α-formyl boronic acids.
Chem Sci 2017;
8:3026-3030. [PMID:
28451370 PMCID:
PMC5380879 DOI:
10.1039/c6sc04522g]
[Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Accepted: 01/28/2017] [Indexed: 01/04/2023] Open
Abstract
An unprecedented enantioselective synthesis of 3-substituted benzoxaboroles has been developed. An in situ generated ortho-boronic acid containing chalcone provides the chiral benzoxaboroles via an asymmetric oxa-Michael addition of hydroxyl group attached to the boronic acid triggered by the cinchona alkaloid based chiral amino-squaramide catalysts. In general, good yields with good to excellent enantioselectivities (up to 99%) were obtained. The resulting benzoxaboroles were converted to the corresponding chiral β-hydroxy ketones without affecting the enantioselectivity.
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