In this study, highly enantioselective copper(I)-catalyzed hydroboration of bicyclic alkenes is reported. Using a copper-taniaphos complex, excellent enantioselectivities up to >99% ee were obtained for bicyclic alkenes including oxa- and azabicyclic alkenes. Furthermore, copper-catalyzed enantiodivergent hydroboration methods with the same chiral ligand-copper precursors were developed using different boron sources based on alternative mechanistic pathways.

Stereospecific cross-coupling of chiral α-borylalkylcopper 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 α-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.

Highly enantioselective, copper-catalyzed ring opening of bicyclic hydrazines using a diboron reagent was accomplished with (R,R)-taniaphos as a chiral ligand. Desymmetrization of various bicyclic hydrazines by boryl substitution afforded 3-Bpin-4-hydrazino-cyclopentene derivatives with enantioselectivity up to >99% under mild conditions. The resulting allylic boron products were utilized in further organic transformations. Kinetic resolution of a racemic bicyclic oxazine gave useful information about the relative rates of C–O and C–N bond cleavage.

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Copper(I)-catalyzed asymmetric 1,6-borylation of 1,3-dienylphosphonates was achieved using (S,S)-Ph-BPE as a chiral ligand. Regio-, stereo-, and enantioselective borylation successfully proceeded to afford phosphonatecontaining allylboronates, with high enantioselectivity up to 97% ee. Further applications of the resulting products generated a valuable phosphonate analogue of γ-butyrolactone.Letter pubs.acs.org/OrgLett