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Metal‐Free Synthesis of Imidazo[2,1‐ b ]thiazoles from Thioimidazoles and Ketones Mediated by Selectfluor
Author(s) -
Zhao Jinwu,
Xiao Qiannan,
Chen Jiaxi,
Xu Jingxiu
Publication year - 2020
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.202000815
Subject(s) - selectfluor , chemistry , thiazole , steric effects , ketone , electrophile , aryl , organic chemistry , medicinal chemistry , reagent , catalysis , alkyl
This paper presents a practical and efficient strategy for the preparation of imidazol[2,1‐ b ]‐thiazoles from thioimidazoles and ketones mediated by Selectfluor. The proposed mechanism suggests that this transformation took place through electrophilic thiolation at an α‐carbon of ketones by sulfur cation, which is produced by the oxidation of thioimidazole by Selectfluor. This metal‐free protocol tolerated various ketones, including methyl ketones or non‐methyl ketones, aryl ketones or aliphatic ketones. The experimental results indicated that steric hindrance of the substituents at the α‐position of ketones or on the aromatic ring of aryl ketones had significant influence on the yields of imidazol[2,1‐ b ]‐thiazoles. Thioimidazole and benzothioimidazoles were well tolerated while 5‐substituted benzothioimidazoles provided the mixture of the corresponding 6‐substituted and 7‐substituted benzoimidazo[2,1‐ b ]thiazole products.