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Iron‐Mediated Oxidative C–H Alkylation of S,S ‐Functionalized Internal Olefins via C( sp 2 )–H/C( sp 3 )–H Cross‐Coupling
Author(s) -
Wang Quannan,
Lou Jiang,
Wu Ping,
Wu Kaikai,
Yu Zhengkun
Publication year - 2017
Publication title -
advanced synthesis and catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.541
H-Index - 155
eISSN - 1615-4169
pISSN - 1615-4150
DOI - 10.1002/adsc.201700654
Subject(s) - chemistry , alkylation , dabco , toluene , ketene , medicinal chemistry , catalysis , oxidative coupling of methane , stereochemistry , organic chemistry
Mediated by a catalytic amount of FeCl 3 , the C–H alkylation of S,S ‐functionalized internal olefins, i.e., α‐oxo ketene dithioacetals and their analogues, was efficiently achieved using simple ethers and toluene derivatives as the coupling partners, di‐ tert ‐butyl peroxide (DTBP) as the oxidant, and DABCO⋅6 H 2 O as the additive. The alkylthio functionality is essential for the internal olefinic C–H bond to undergo such an alkylation with the O ‐adjacent C(sp 3 )–H bonds of the ethers and the benzylic C–H bonds of the toluene derivatives, respectively. Tetrasubstituted olefins were thus synthesized and further transformed to highly substituted pyrazoles and isoxazoles. The strategy to activate an internal olefinic C–H bond by polarizing its parent olefinic C=C bond with both the dialkylthio group and an electron‐withdrawing functionality was investigated. The mechanistic studies suggest a radical pathway for the C( sp 2 )–H/C( sp 3 )–H cross‐coupling reactions. The present protocol provides a convenient route to tetrasubstituted olefins.