α-Boryl Organometallic Reagents in Catalytic Asymmetric Synthesis

Abstract

Recent years have witnessed an increase in the popularity of α-boryl organometallic reagents as versatile nucleophiles in asymmetric synthesis. These compounds have been adopted in chemo- and stereoselective coupling reactions with a number of different electrophiles. The resulting enantioenriched boronic esters can be applied in stereospecific carbon–carbon or carbon–heteroatom bond construction reactions, enabling a two-step strategy for the construction of complex structures with high efficiency and functional group compatibility. For these reasons, tremendous effort has been devoted to the preparation of enantiomerically enriched α-boryl organometallic reagents and to the development of stereoselective reactions of related racemic or prochiral materials. In this review, we describe enantio- or diastereoselective reactions that involve α-boryl organometallic reagents as starting materials or products and showcase their synthetic utility.

Enantioselective Suzuki cross-coupling of 1,2-diboryl cyclopropanes

“…6 In this context, the development of enantioselective Suzuki–Miyaura cross-coupling reactions using prochiral bis-boronates remains largely unexplored. 7,8 Morken 9 and Hall 10 reported the enantioselective Suzuki cross-coupling reaction of symmetric geminal bis-boronates to prepare enantiomerically enriched boronic esters (Fig. 1a).…”

Asymmetric Syntheses of (Z)- or (E)-β,γ-Unsaturated Ketones via Silane-Controlled Enantiodivergent Catalysis

“…In this context, chiral nonracemic, acyclic β,γ-unsaturated ketones with an α-tertiary stereocenter (e.g., A in Scheme ) are of great importance. Such entities are common scaffolds in bioactive natural products, , and more importantly, the functional groups embedded in these molecules provide useful handles for further derivatization . However, several challenges exist for asymmetric syntheses of chiral nonracemic acyclic β,γ-unsaturated ketones A .…”

1,2-Diborylsilanes: Catalytic Enantioselective Synthesis and Site-Selective Cross-coupling

“…Despite the large size of silanes, the elongated Si–C bond distance reduces steric hindrance while still offering electronic modulation of reactivity due to the α and β silicon effect. These unique properties offer useful reactivity to silylboronate intermediates, especially geminal borylsilylalkanes . It was hypothesized that a chiral trifunctional diborylsilylalkane might allow sequential functionalization, thereby affording useful routes to enantiomerically enriched building blocks.…”

“…These unique properties offer useful reactivity to silylboronate intermediates, especially geminal borylsilylalkanes. 13 It was hypothesized that a chiral trifunctional diborylsilylalkane might allow sequential functionalization, thereby affording useful routes to enantiomerically enriched building blocks. Pioneering investigations by Yun showed that these reagents could be prepared by enantioselective Cu-catalyzed double borylation of silylacety-lenes (Figure 1a).…”