Photoredox-Catalyzed C–H Arylation of Internal Alkenes to Tetrasubstituted Alkenes: Synthesis of Tamoxifen

Visible-light-induced
direct C–H arylation of S,S-functionalized
internal alkenes, that is, α-oxo ketene dithioacetals
and analogues, has been efficiently realized with aryldiazonium salts
(ArN2BF4) as coupling partners and Ru­(bpy)3Cl2·6H2O as photosensitizer at
ambient temperature. The strategy to activate the internal olefinic
C–H bond by both the alkylthio and electron-withdrawing functional
groups was investigated. The synthetic protocol was successfully applied
to the synthesis of all-carbon tetrasubstituted alkenes including
tamoxifen.