Microwave-enhanced rhodium-catalyzed conjugate-addition of aryl boronic acids to unprotected maleimides

Various boronic acids were treated with a rhodium(I) catalyst enabling their 1,4-conjugate addition to unprotected maleimide. The scope of the reaction was explored to include both electron-rich and electron poor boronic acids. These reactions were also performed in the microwave resulting in reduced reaction times and improved efficiencies. Additionally, substrates that were recalcitrant under conventional conditions were successfully reacted under microwave conditions. The reaction worked satisfactorily with boronic acids having a free OH or NH group.