Synthesis of branched and linear aryl allylic alcohols: CH bond allylation of 2-aryl-3H-indoles with vinyl cyclic carbonates

Presented herein is an effective synthesis of branched and linear allyl arenes based on the reactions of 2-aryl-3H-indoles with 5-methylene-1,3-dioxan-2-one or 4-vinyl-1,3-dioxolan-2-one. Mechanistically, the reactions are initiated by Rh(III)-catalyzed aryl C(sp²)–H bond activation/cyclometallation followed by vinyl coordination/migratory insertion and β–O elimination through release of CO₂ as the only by-product. By using this newly developed protocol, a group of 2-aryl-3H-indole derivatives bearing the substructure of either branched or linear allylic alcohol were obtained in good efficiency. Notably, the linear allylic alcohols were obtained with excellent E/Z selectivity when unsubstituted vinyl-1,3-dioxolan-2-one was used as the allyl surrogate. With advantages such as easily available starting materials, mild and redox-neutral reaction conditions, good compatibility with a broad range of functional groups, benign solvent and divergent products, this protocol is expected to be used in the synthesis of indole-based functional molecules.