Mostardeiro VB, Dilelio MC, Kaufman TS, Silveira CC. Efficient synthesis of 4-sulfanylcoumarins from 3-bromo-coumarins
via a highly selective DABCO-mediated one-pot thia-Michael addition/elimination process.
RSC Adv 2020;
10:482-491. [PMID:
35492534 PMCID:
PMC9047558 DOI:
10.1039/c9ra09545d]
[Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Accepted: 12/18/2019] [Indexed: 01/07/2023] Open
Abstract
A facile and efficient protocol for the highly selective direct sulfanylation of 3-bromocoumarins under DABCO promotion, was developed. The transformation took place with aromatic and aliphatic thiols as well as with α,ω-dithiols, affording the expected products in very good to excellent yields. Simple and convenient ways to access 4-((ω-mercaptoalkyl) thio)coumarins and the dimeric 4,4′-(alkane-1,4-diylbis(sulfanediyl))bis(coumarins) were also devised with the use of α,ω-alkanedithiols in different ratios with regards to the starting 3-bromocoumarin. The transformation seems to proceed through the DABCO-mediated thia-Michael stereoselective addition of the thiolate anion to the α,β-unsaturated carbonyl system of the coumarin, followed by a DABCO-assisted stereoselective dehydrobromination of the resulting α-bromo carbonyl intermediate.
A facile, simple and metal-free protocol for the 4-sulfanylation of 3-bromocoumarins was developed. It involves a thia-Michael addition and a dehydrobromination under DABCO assistance.![]()
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