Metal-Free Stereoconvergent C-H Borylation of Enamides

Enamides, functional derivatives of enamines, play a significant role as synthetic targets. However, the stereoselective synthesis of these molecules has posed a longstanding challenge in organic chemistry, particularly for acyclic enamides that are less thermodynamically stable. In this study, we present a general strategy for constructing beta-borylenamides by C-H borylation, which provides a versatile platform for generating the stereodefined enamides. Our approach involves the utilization of metalloid borenium cation, generated through the reaction of BBr3 and enamides in the presence of two different additives, avoiding any exogenous catalyst. Importantly, the stereoconvergent nature of this methodology allows for the use of starting materials with mixed E/Z configurations, thus highlighting the unique advantage of this chemistry. Mechanistic investigations have shed light on the pivotal roles played by the two additives, the reactive boron species, and the phenomenon of stereoconvergence. A novel method is presented for synthesizing beta-borylenamides through C-H borylation, providing a versatile means of creating stereodefined enamides. The remarkable feature of this methodology is its stereoconvergent nature, which enables the utilization of starting materials with both E and Z configurations.+image

Automated summary

This study presents a general strategy for constructing beta-borylenamides through C-H borylation, which provides a versatile means of creating stereodefined enamides. The unique advantage of this methodology lies in its stereoconvergent nature, allowing for the utilization of starting materials with both E and Z configurations.