Alkene difunctionalization constitutes a powerful approach for rapidly attaining complex molecular scaffolds from simpler and more widely available compounds. Cu/Pd-catalyzed carboboration is an effective method for this, as it allows for the simultaneous establishment of a carbon-carbon bond and versatile carbon-boron bond. Previously, our group has demonstrated the utility of this dual catalytic system for arylboration through diastereoselective and enantioselective variants with 1,1- and 1,2-disubstituted styrene derivatives. Recently, we have developed an efficient approach towards accessing Type III bifunctional allylation reagents via Cu/Pd-catalyzed alkenylboration of alkenylboronamide derivatives (dan = 1,8-diaminonaphthalene). These types of double-allylation reagents allow for the rapid construction of highly complex diols in an expedient fashion. Notable aspects of the strategy include 1) a broad alkenylboration substrate scope that includes di-, tri-, and tetra-substituted vinylhalide electrophiles; 2) the alkenylboration can be done in a diastereoselective, enantioselective, and stereodivergent manner, providing a variety valuable allylation precursors; 3) novel use of an allylBdan directly in a stereocontrolled allylation without initial deprotection to the boronic ester; and 4) a stereocontrolled second allylation to access complex 1,4-diol motifs with multiple contiguous stereocenters. Furthermore, mechanistic investigations provide insight into how the unique interplay between alkene geometry and the ligand environments of Cu/Pd result in diastereodivergent reactivity. Overall, the modularity and the ease in which complex structural motifs can be accessed in a rapid manner signify the importance and utility of this method.

Cu/Pd-catalyzed alkenylboration: Rapid and modular access to a versatile double-allylation reagent

ACS Fall 2021

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