Ionic liquids as solvent for regioselective arylation of α-substituted allylic alcohols by aryl bromides

Regioselective Heck arylation of α-substituted allylic alcohols by aryl bromides was achieved by Pd-DPPP catalysis in ionic liquids, affording a β/γ ratio of up to 78/22 in the case of the coupling of 1-bromonaphthalene with but-1-en-3-ol. In addition to the effects of both ligands and reaction media, the regiocontrol toward the formation of branched products was significantly affected by the steric properties of allylic alcohols; with the increasing bulkiness of the substituent on allylic alcohol, the β/γ regioselectivity decreased. For comparison, arylation by aryl triflates in a molecular solvent was also demonstrated, which showed the same trend in regioselectivity.

Graphical abstractIonic liquid is shown to promote the Pd-DPPP catalyzed regioselective Heck arylation of α-substituted allylic alcohols by aryl bromides, affording β/γ ratios of up to 78/22.Figure optionsDownload full-size imageDownload as PowerPoint slide