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Radical Bromocyclization of Alkynes for the Synthesis of Thio-Flavonoids and Benzothiophenes
Gang Yang1, Han Zhang1, Zeng Han1
1Engineering Research Centre of Molecular Medicine of Ministry of Education, Key Laboratory of Fujian Molecular Medicine, Key Laboratory of Precision Medicine and Molecular Diagnosis of Fujian Universities, Key Laboratory of Xiamen Marine and Gene Drugs, School of Biomedical Sciences, Huaqiao University, Xiamen 361021, P. R. China.
Abstract:
A highly efficient and versatile strategy has been developed for the synthesis of 3-brominated thioflavonoids and benzothiophenes from readily available alkynes by using tetrabutylammonium bromide (TBAB) as the bromine source. This transformation proceeds smoothly via photocatalyzed, regioselective bromination/cyclization under metal- and additive-free conditions, with excellent functional group tolerance. This protocol enables the efficient construction of biologically relevant brominated heterocycles in up to 99% yield for 37 examples, thus offering a valuable protocol for directly introducing bromine into diverse thioflavonoids and benzothiophenes.
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