Decarboxylative alkylation of alkenes

Arenes and alkenes share the presence of C( sp 2 )–H bonds of similar bond dissociation energy, yet their reactivity differs fundamentally. Arenes undergo electrophilic substitution because of aromatic stabilization, for example, in Friedel–Crafts alkylation. By contrast, alkenes react by electrophilic addition (Fig. 1a ), which prevents analogous substitution chemistry, so there is no alkene analogue to Friedel–Crafts alkylation, and the general alkylation of alkenes remains unknown. Current strategies for substituted alkene synthesis commonly rely on alkenation reactions such as the Wittig 4 , Horner–Wadsworth–Emmons (HWE) 5 , 6 and Julia protocols 7 , which proceed from carbonyl compounds. Reductive alkylation of alkynes 8 , 9 , 10 offers an alternative. Alkene cross-metathesis provides a formal alkylation pathway directly from alkenes by transalkenylidination, but the types of alkene suitable for cross-metathesis with one another must be carefully selected, and the reaction is restricted to alkene pairs of appropriate reactivity 11 . Moreover, E -selective cross-metathesis of 1-alkenes and 1,1-di-substituted alkenes remains unknown, and several alkene classes, such as tri-substituted and cyclic alkenes, cannot be alkylated with alkene metathesis at all due to the mechanism-based alkylidene transfer that breaks the C=C double bond before a new one is formed 12 , 13 , 14 . …