Methyl-Selective Radical Sorting for the Regio- and Stereoselective Dialkylation of Activated Alkenes

Abstract

The regioselective incorporation of two alkyl radicals across alkenes is an attractive strategy for C(sp3)–C(sp3) bond construction, but remains difficult when the radical partners have similar polarity and limited steric differentiation. Here we report a photoinduced nickel-catalyzed strategy for the regio- and cross-selective 1,2-dialkylation of activated alkenes, including electron-poor olefins and styrenes, in which a methyl group and a second alkyl fragment are installed at defined, complementary positions across the C═C bond. The process relies on iodine(III) carboxylates, either preformed or generated in situ from the corresponding carboxylic acids, as alkyl-radical precursors, enabling the concurrent formation of a methyl radical and a second alkyl radical under the same reaction conditions. Selectivity arises from a radical-sorting process in which a Ni(II) catalyst captures a methyl radical to generate a high-valent Ni–Me intermediate, while the second alkyl radical undergoes Giese-type addition to the activated alkene, followed by SH2 C(sp3)–C(sp3) coupling to deliver the cross-dialkylated product. The method accommodates secondary and tertiary alkyl radicals and, importantly, also differentiates methyl from primary alkyl radicals, with broad functional group tolerance and compatibility with complex molecules. Mechanistic experiments support this radical-sorting model. Finally, chiral auxiliary-substituted alkenes enable highly diastereoselective variants, extending this radical sorting strategy to the synthesis of enantioenriched products.