Catalytic Asymmetric Conjugate Addition of a Borylalkyl Copper Complex for Chiral Organoboronate Synthesis

Abstract

We report the catalytic enantioselective conjugate addition of a borylalkyl copper nucleophile generated in situ from a 1,1‐diborylmethane derivative to α,β‐unsaturated diesters. In the presence of a chiral N‐heterocyclic carbene (NHC)–copper catalyst, this method facilitated the enantioselective incorporation of a CH2Bpin moiety at the β‐position of the diesters to yield β‐chiral alkyl boronates in up to 86 % yield with high enantioselectivity. The alkylboron moiety in the resulting chiral diester products was converted into various functional groups by organic transformation of the C−B bond.

α-Boryl Organometallic Reagents in Catalytic Asymmetric Synthesis

“…The deborylative conjugate addition of diborylmethane species was also reported. Jang and Yun utilized a chiral Cu–NHC complex as the catalyst to accomplish a highly selective and efficient conjugate addition reaction with α,β-unsaturated diesters 62 (Scheme a) . During this process, an alkylcopper intermediate can selectively add to the Re face of the alkene.…”

“…Jang and Yun utilized a chiral Cu− NHC complex as the catalyst to accomplish a highly selective and efficient conjugate addition reaction with α,β-unsaturated diesters 62 (Scheme 22a). 42 During this process, an alkylcopper intermediate can selectively add to the Re face of the alkene. In the presence of an adjacent stereogenic center, matched and mismatched cases were observed.…”

Boron-promoted Deprotonative Conjugate Addition: Development of Geminal diborons as Versatile Soft Pronucleophiles and Acyl An-ion Equivalents

“…13b Despite the above advances, the full synthetic potential of α-boryl carbanion-based conjugate additions remain untapped. For instance, majority of the currently available methods for 1,4-addition of α-boryl carbanions involve deborylation of geminal triboryl 9 and diboryl 13 alkanes besides requiring activation by neighboring benzylic, 9 allylic 11 or Cu 10,13 groups (Figure 1a-d). In contrast, general strategies for conjugate addition of α,α-diboryl stabilized carbanions produced by deprotonation of geminal diborons lacking any other electron-withdrawing groups remain scarce.…”

Chemodivergent transformations of amides using gem-diborylalkanes as pro-nucleophiles

“…Therefore, the development of strategies for chemodivergent transformation of simple amides, including primiary amides, secondary amides, and tertiary amides, remains undeveloped. 1,1-Diborylalkanes as a special type of gem-dimetallic compounds have drawn much attention in organic synthesis in recent years, and many efforts on the synthesis of this type of compounds make them easily accessible [30][31][32][33][34][35][36][37] . Generally, 1,1-diborylalkanes could provide α-boryl carbanion synthons via deprotonation or Lewis base coordination.…”