Amphiphilic [pi]-allyliridium catalyzed nucleophilic and electrophilic allylation
Transition metal-catalyzed allylic substitution has emerged as a powerful method for stereoselective C-N bond formation. Chiral iridium-phosphoramidite complexes have proven especially effective as catalysts for regio- and enantioselective allylic amination, but are limited to aryl-substituted π-allyl electrophiles. With commercially available π-allyliridium C,O-benzoates, which are stable to air, water and SiO₂ chromatography, and are well known to catalyze allylic acetate mediated carbonyl allylation, highly regio- and enantioselective electrophilic allylation of aliphatic amines, primary and secondary aromatic or heteroaromatic amines were demonstrated. Furthermore, indoles and related azoles can also undergo the amination and generate enantiomerically enriched N-allyl indoles with completely N-selective and exclusive branched regioselectivity, which are an unmet challenge in this field. Moreover, indoles and related azoles are prevalent structural motifs in clinical candidates and FDA approved drugs, so these results also show the utility and importance of asymmetric allylic alkylation.