Construction of α-Halogenated Boronic Esters via Visible Light-Induced C–H Bromination

Abstract

α-Halogenated boronic esters are versatile building blocks that can be diversified into a wide variety of polyfunctionalized molecules. However, their synthetic potential has been hampered by limited preparation methods. Herein, we report a visible light-induced C−H bromination reaction of readily available benzyl boronic esters. This method features high yields, mild conditions, simple operation, and good functional group tolerance. The analogous chlorides and iodides can be accessed via Finkelstein reaction. Synthesis of halogenated geminal diborons has also been demonstrated.

A General Method to Access Sterically Encumbered Geminal Bis(boronates) via Formal Umpolung Transformation of Terminal Diboron Compounds

“…Sterically encumbered, ortho-substituted products, which are challenging to prepare by other reported methods, could be furnished at elevated temperatures (18 and 19). This protocol also exhibited high tolerance to functional groups such as alkenes, nitrile, ester, and bromo groups (20)(21)(22)(23)(24)(25). Moreover, naphthalene, a wide variety of aromatic heterocycles, and complex frameworks derived from drug molecules were all found to be suitable components (26)(27)(28)(29)(30)(31)(32)(33)(34)(35), showing the potential for late-stage functionalization.…”

“…The success of 77 encouraged us to streamline the synthesis of diaryl gem-diboron compounds by combining two substitution steps and the photoinduced bromination reaction developed by our group. [22] Diaryl gembis(boronates) can serve as synthons for gem-diaryl moieties, which are widespread in pharmacophores [23] and functional material molecules. [24] As illustrated in Table 4, starting from diborylmethyl chloride (53), a "substitutionbromination-substitution" sequence allowed the rapid as-…”

A General Method to Access Sterically Encumbered Geminal Bis(boronates) via Formal Umpolung Transformation of Terminal Diboron Compounds

“…The success of 77 encouraged us to streamline the synthesis of diaryl gem ‐diboron compounds by combining two substitution steps and the photoinduced bromination reaction developed by our group [22] . Diaryl gem ‐bis(boronates) can serve as synthons for gem ‐diaryl moieties, which are widespread in pharmacophores [23] and functional material molecules [24] .…”

“…The success of 77 encouraged us to streamline the synthesis of diaryl gem-diboron compounds by combining two substitution steps and the photoinduced bromination reaction developed by our group. [22] Diaryl gembis(boronates) can serve as synthons for gem-diaryl moieties, which are widespread in pharmacophores [23] and functional material molecules. [24] As illustrated in Table 4, starting from diborylmethyl chloride (53), a "substitutionbromination-substitution" sequence allowed the rapid as- sembly of the final products with a diverse array of aryl groups (78-86).…”