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- Title
New Synthesis of Thioflavanones by the Regioselective Cyclization of 1‐(2‐Benzylthio)phenyl‐3‐phenyl‐2‐propen‐1‐ones with Hydrobromic Acid.
- Authors
In Lee, Jae
- Abstract
Keywords: Thioflavanones, Condensation, 6-Endo cyclization EN Thioflavanones, Condensation, 6-Endo cyclization 484 487 4 04/20/20 20200401 NES 200401 GLO:1CJF/01apr20:bkcs11989-toc-0001.jpg PHOTO (COLOR): . gl Thioflavanones have a skeleton of a thiochroman-4-one ring with aryl groups in the 2-position and unlike flavanones are not found naturally. Initially, 1-(2-benzylthio)phenylethanone ( B 2 b ) was prepared in two steps: (1) The reaction of 2-mercaptobenzoic acid ( B 1 b ) and 3 equiv. of methyllithium in THF afforded 2'-mercaptoacetophenone in 81% yield. The cyclization of B 3h b with CF SB 3 sb COOH solvent and 5 equiv. of 70% HClO SB 4 sb in THF afforded 4'-methoxythioflavanone ( B 4 h b ) in 90% and 45% yield, respectively, in 4 h/70 °C and 24 h/65 °C, respectively (entries 2-3). On the other hand, the cyclization of B 3h b proceeded well with 1.5 equiv. of 48% HBr in CH SB 3 sb CN to give B 4h b in 93% yield after 1 h at 70 °C (entry 4).
- Subjects
HYDROBROMIC acid; BENZYL chloride; BENZYL bromide; OXALYL chloride; DICHLOROMETHANE
- Publication
Bulletin of the Korean Chemical Society, 2020, Vol 41, Issue 4, p484
- ISSN
0253-2964
- Publication type
Article
- DOI
10.1002/bkcs.11989