Reports: AC1
46269-AC1 A Modular Approach Chiral NHC Ligands and Their Use in Asymmetric Catalysis
Our PFR grant funded the development of a new one-pot route to N-heterocyclic carbenes. Ligands from this work were then used in a number of pilot reactions with the most success coming with the reaction in the palladium-catalyzed reaction between iodo phenols and azabicyclic alkenes.
We have found that palladium N-heterocyclic carbene (NHC) complexes are effective catalysts for the reaction reported by Radhakrishnan. Palladium IPr complexes catalyze the reaction with iodo phenols with azabicyclic alkenes in good yield. The reaction proceeds with either normal heating or with microwave heating. Using the microwave the reaction times are 30 minutes and the reaction proceeds with as little as 2 mol % catalyst. To date we have not been successful getting the reaction with iodo anilines to run with a palladium NHC catalysts but we are continuing to develop this method. The original report requires the use of ionic solvents or at lease additives such as Bu4NCl.
A variety of reactions conditions were investigated to determine the best reaction conditions. DMF appears to the best solvent providing product in over 95% yield using 1 mol % catalysts under microwave heating. Using these conductions the reaction proceeds on the variety of different iodo phenols, including versions that possess heteroatoms and other acidic protons.
