Efficient and environmentally-friendly access to 4,5-unsaturated sulfonamides through ligand-free copper-BF3-catalyzed three-component alkene carbo-sulfonamidation

Abstract

Though sulfonamides are biologically important molecules, the scope of their structures is narrow due to the limited methods available for their syntheses. Alkene functionalization has recently gained attention for the synthesis of sulfonamides due to the easy availability of alkenes and their diverse reactions. These alkene reactions, however, experience either regioselectivity problems and/or require the use of stoichiometric quantities of reagents. We present a new, environmentally-friendly method for the synthesis of 4,5-unsaturated sulfonamides from aryl-substituted alkenes, allylic alcohols, and commercially available sulfonamides through alkene functionalization by employing a copper(I)-BF₃ pair as a catalyst. We showed that this catalyst plays a dual role in stabilizing allyl cations and activating alkenes. Different allylic alcohols, arylalkenes, and sulfonamides were found to be compatible with the optimized reaction conditions, allowing the generation of the desired products with reasonably good yields (60–90%). Further structural manipulations of the products are possible due to the presence of an unsaturated double bond and/or reactive functional groups such as aryl bromide and benzyl chloride.