Regio- and enantioselective C-C and C-N bond formations catalyzed by amphiphilic [pi]-allyliridium C,O-benzoate complexes




Jung, Woo-Ok

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Enantioselective nucleophilic and electrophilic allylations mediated by racemic branched allylic acetates and catalyzed by π-allyliridium C,O-benzoate complexes are described. The π-allyliridium C,O-benzoate-catalyzed reductive coupling of the commodity chemical allyl acetate with acetylenic ketones mediated by 2-propanol to form enantiomerically enriched tertiary propargyl alcohols was developed. The same π-allyliridium C,O-benzoate complexes were found to be competent catalysts for the enantioselective electrophilic allylations of secondary amines and α,α-disubstituted nitronates, delivering tertiary allylic amines and (after zinc-mediated reduction of the nitroalkane) β‑stereogenic α‑quaternary primary amines, respectively. These processes form hindered C-C and C-N bonds with complete levels of branched regioselectivity. Attempted use of linear allyl acetates in the aforesaid processes provided products hydroamination instead of the expected products of Tsuji-Trost-type allylation. As revealed by deuterium labelling studies, chelation of the iridium catalyst to the internal olefin and the acetate carbonyl played a key role in partitioning the hydroamination vs allylation pathways and directing the regioselectivity of hydroamination.



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