Heck-type coupling vs. conjugate addition in phosphine–rhodium catalyzed reactions of aryl boronic acids with α,β-unsaturated carbonyl compounds: a systematic investigation
Heck-type coupling and conjugateaddition by synergistically tuning the supporting ligand, the boronic acid to olefin ratio and other reaction conditions. Conjugateaddition with selectivity >99% and Heck-type coupling with selectivity of up to 100%, 98% and 84% for acrylates, acrylamides and methyl vinyl ketone, respectively, could be achieved in the rhodium-catalyzed reactions of aryl boronic acids
1,4-Addition of arylboronicacids to acrylic acid derivatives proceeds efficiently in the presence of a palladium catalyst system of Pd(OAc)2/(PhO)3P to produce the corresponding 3-arylpropionic acid derivatives. The use of the phosphite ligand is the key to conducting the addition smoothly with suppressing the competing Mizoroki−Heck-type oxidativecoupling.
Rhodium fluoroapatite (RhFAP) is an efficient catalyst for conjugateaddition of organoboron reagents to α,β-unsaturated carbonyl compounds. A variety of arylboronic acids and α,β-unsaturated carbonyl compounds were converted to the corresponding conjugate-addition products, demonstrating the versatility of the reaction. The reaction is highlyselective. RhFAP was recovered quantitatively by simple filtration