Pd-Catalyzed Stereospecific Cross-Coupling of Chiral α-Borylalkylcopper Species with Aryl Bromides

Stereospecific cross-coupling of chiral alpha-borylalkyl-copper species with aryl bromides has been achieved using a Pd catalyst. The combination of a copper catalyst and chiral NHC ligand was efficient for the generation of enantioenriched secondary alpha-borylorganocopper species via addition of a Cu-Bpin (= pinacol boronic ester) species to alkenyl boramides. Subsequent stereospecific cross-coupling of such organocopper nucleophiles with aryl bromides successfully proceeded with a palladium-XPhos catalyst. Using 1,2-disubstituted borylalkenes containing a 1,8-naphthalenediaminatoboryl (Bdan) group produced the corresponding anti-diborylalkanes as a single diastereomer with good enantioselectivity up to 96.5:3.5 er, and subsequent oxidation generated the corresponding anti-1,2-dihydroxyl compounds.