Allylboronates from Vinyl Triflates and α-Chloroboronates by Reductive Nickel Catalysis

Abstract

Allylboronates are unique building blocks widely used in organic synthesis, but the construction of cyclic allylboranates remains a challenging subject. We demonstrate here a mild and efficient access to this type of compound through the cross-electrophile coupling of vinyl triflates and α-chloroboronates. The reaction proceeded with a good substrate scope and good functional group compatibility. The ready availability of vinyl triflates from ketones, as well as the rich chemistry of allylboranates, makes our method suitable for the divergent modification of biologically active compounds. Preliminary mechanistic studies revealed that α-chloroboronates were activated via a radical process.

Reductive Cross-Coupling of Vinyl Electrophiles

“…In 2020, we demonstrated a mild and efficient access to this type of compound through the cross-electrophile coupling of vinyl triflates and -chloroboronates (Scheme 13b). 44 The reaction proceeded with good substrate scope and good functionality tolerance. The ready availability of vinyl triflates from ketones, as well as the rich chemistry of allylboronates, makes this method suitable for the divergent modification of biologically active compounds.…”

Recent Advances in Nonprecious Metal Catalysis

“…Allylboronates are considered another attractive coupling partner that can be accessed via Ni catalysis. Following the recent elegant work of Sun and Martin on the development of chemoselective arylation and alkylation of amphoteric α-haloboronates with aryl bromides or vinyl bromides, Shu and co-workers demonstrated efficient access to allylboronates through reductive Ni-catalyzed cross-electrophile coupling of α-chloroboronates with vinyl triflates in moderate to good yields (Scheme ). The reaction demonstrates good functional group tolerance and substrate scope, including cyclic and heterocyclic trisubstituted vinyl triflates.…”

“…Allylboronates are considered another attractive coupling partner that can be accessed via Ni catalysis. Following the recent elegant work of Sun and Martin 26 on the development of chemoselective arylation and alkylation of amphoteric αhaloboronates with aryl bromides or vinyl bromides, Shu and co-workers 27 Arylboronic esters are extensively used as key coupling partners in organic synthesis in both drug discovery and process chemistry. Easy access to these compounds remains of interest in many research groups.…”

A Pd-catalyzed organometallic-free homologation of arylboronic acids enabled by chemoselective transmetalation

“…Halomethylorganoboron reagents have been shown to display several different reactivity profiles, including metalation, boronate formation, and the formation of a-boryl radicals; however, examples of oxidative addition to this reagent class remain rare and are principally achieved using Ni catalysis. For example, Fu demonstrated stereoconvergent crosscoupling of racemic a-chloroboronic acid esters with organozinc reagents, 40,41 while Martin first showed crosselectrophile coupling [42][43][44] and alkene difunctionalization using a-bromoboronic acid esters. 45 Within Pd catalysis, Gevorgyan has developed Heck reactions based on a single-electron transfer (SET) manifold.…”