We report broadly applicable copper catalytic conditions for the diastereoselective and enantioselective 1,2addition of 1,1-diborylalkanes to cyclic ketimines and α-imino esters. The developed method provides various β-aminoboronate esters bearing adjacent stereocenters with high diastereo-and enantioselectivity. Synthetic applications for converting the obtained β-aminoboronate esters to a diverse array of synthetically useful chiral compounds are demonstrated.

We report a copper-catalyzed enatiotopic-groupselective allylation of gem-diborylalkanes with allyl bromides. The combination of copper(I) bromide and H 8 −BINOL derived phosphoramidite ligand proved to be the most effective catalytic system to provide various enantioenriched homoallylic boronate esters, containing a boron-substituted stereogenic center that is solely derived from gem-diborylalkanes, in good yields with high enantiomeric ratios under mild conditions. Experimental and theoretical studies have been conducted to elucidate the reaction mechanism, revealing how the enatiotopic-group-selective transmetalation of gem-diborylalkanes with chiral copper complex occurs to generate chiral α-borylalkyl-copper species for the first time. Additional synthetic applications to the synthesis of various chiral building blocks are also included.

Reported herein is the utilization of bis-[(pinacolato)boryl]methylzinc halides, whose structures are characterized via single-crystal X-ray analysis, as solid storable reagents for copper-catalyzed coupling with vinyliodonum salts. The reaction proceeds under mild conditions and shows broad scope with respect to vinyliodonium salts, affording various αboryl-substituted allylboronate esters in good yields. Synthetic applications of the obtained products are also demonstrated.O rganoborons are undoubtedly one of the most important classes of intermediates that are widely utilized in agroscience, material science, and medicinal chemistry. 1 Among them, allylboron compounds have attracted significant attention over the past decades, because they serve as versatile synthons in several organic transformations such as 1,2addition, allylboration, and Suzuki−Miyaura cross-coupling. 2 Consequently, extensive efforts have been devoted to the preparation of allylboron reagents; however, most of the methods are primarily concentrated on synthesizing monoboron-containing allylic compounds. 2,3 Recently, α-boryl-substituted allylboronate esters have emerged as new types of allylboron reagents. Such reagents are especially appealing, because they can undergo highly chemo-and stereoselective allylboration with aldehydes and cyclic aldimines to give δ-boryl-substituted homoallylic alcohols or amines, which allow further manipulations of the alkenyl moiety. 4 Nonetheless, a few examples have been reported for the preparation of α-boryl-substituted allylboronate esters (Scheme 1a). Wang and co-workers described a transition-metal-free coupling of α,β-unsaturated N-tosylhydrazone with B 2 pin 2 to afford a cyclic α-boryl-substituted allylboronate ester, although they included only one example. 4a Transition-metal-catalyzed double-bond transposition of homoallylic gem-diboronate esters was also developed by Murakami and Miura, 4b−d Chen, 4e and our research group. 4f However, most reagents were generated in situ before use probably because of the equilibration between homoallylic gem-diboronate esters and α-boryl-substituted allylboronate esters. In these studies, only (E)-or (Z)-α-boryl-substituted crotylboronate ester could be selectively isolated. Chen and coworkers disclosed a nickel-catalyzed 1,4-diboration of dienylboronate ester to afford (Z)-α,δ-bisboryl crotylboronate esters. 5 More recently, Meek et al. reported Pd-catalyzed crosscoupling of bis[(pinacolato)boryl]methyl lithium and β,β-

Catalytic enantioselective conjugate additions of simple alkyl groups to nitroalkenes or cyclic enones that result in the formation of tertiary C–C bonds are described. For these stereoselective addition reactions, new chiral phosphino‐oxazoline ligands were synthesized and used. The reactions were promoted by a Cu‐based catalyst (2 mol‐%), and gave the chiral products in up to 92 % yield with 95 % ee. A larger‐scale synthesis was demonstrated, and the origin of the stereoselectivity was proposed based on DFT calculations.