An iridium-catalyzed enantioconvergent coupling of the versatile
boron-stabilized organozinc reagent BpinCH2ZnI with a racemic
branched allylic carbonate has been developed here, which differs
from our previous work by using 1,1-bisborylmethane through the kinetic
resolution process. The reaction has a broad substrate scope, and
various chiral homoallylic organoboronic esters could be obtained
in good yields with excellent enantioselectivities. The synthetic
practicability of the products was demonstrated by their conversion
to other useful families of compounds.
Nickel-catalyzed cross-coupling of unactivated tertiary alkyl electrophiles with alkylmetal reagents is still a challenge. We report herein a nickel-catalyzed Negishi cross-coupling of alkyl halides, including unactivated tertiary halides, with boron-stabilized organozinc reagent BpinCH 2 ZnI, yielding versatile organoboron products with high functional-group tolerance. Importantly, the Bpin group was found to be indispensable for accessing the quaternary carbon center. The synthetic practicability of the prepared quaternary organoboronates was demonstrated by their conversion to other useful compounds.
A general and efficient strategy for the preparation of β-branched organoboron compounds through Ni-catalyzed coupling of BpinCH2ZnI with alkyl halides had been developed. In comparison with known methods such as Matteson homologation and the functionalization of 1,1-bisborylmethane, this reaction is more step-economical and has broader functional-group compatibility. Primary, secondary and the challenging tertiary alkyl halides are appropriate substrates to accomplish this transformation. The synthetic practicability of the prepared β-quaternary organoboronates was demonstrated by their conversion to other useful compounds.
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