Preparation of Alkylmagnesium Reagents from Alkenes through Hydroboration and Boron–Magnesium Exchange

Abstract

Tolerant: Alkylmagnesium reagents can be synthesized from alkenes through a sequence of hydroboration and subsequent boron–magnesium exchange using a method that tolerates different functional groups (see scheme). The resulting alkylmagnesium reagents can be used in carbon–carbon bond forming reactions, such as alkylation reactions or transition‐metal‐catalyzed cross‐coupling reactions.

Alkynes as Electrophilic or Nucleophilic Allylmetal Precursors in Transition‐Metal Catalysis

“…This synthesis also utilizes several other methods developed by the Breit group,including the stereospecific zinc-catalyzed crosscoupling of a-hydroxy ester triflates with Grignard reagents [25] and hydroboration-magnesium exchange. [26] Mechanistic studies involving both experimental and computational methods corroborate the indicated catalytic cycle for the rhodium-catalyzed alkyne-based Tsuji-Trost reaction (Scheme 9). [16f] Ther hodium chloride dimer modi-fied by DPEphos dissociates to form amonomer,which in the presence of the terminal alkyne forms the h 2 -alkyne complex C.T he carboxylic acid binds to the rhodium center, thereby forming ar ather stable hydrogen bond to the terminal sphybridized carbon atom.…”

“…This synthesis also utilizes several other methods developed in the Breit laboratory, including the stereospecific zinc-catalyzed cross-coupling of α-hydroxy ester triflates with Grignard reagents [25] and hydroboration-magnesium exchange. [26] …”

Synthesis of Exocyclic Trisubstituted Alkenes via Nickel‐ Catalyzed Kumada‐Type Cross‐Coupling Reaction of gem‐ Difluoroalkenes with Di‐Grignard Reagents

“…To a solution of gem ‐difluoroalkene (1.0 mmol) and 4 mol% NiCl 2 (dppp) (21.7 mg) in THF (5 mL) was added dropwise a solution of the freshly prepared di‐Grignard reagent in THF (1.5 mmol, 0.5 M)18 at room temperature under an argon atmosphere. The mixture was stirred for 0.5–1 h at room temperature (monitored by TLC and GC/MS).…”

Recent advancements on the use of 2-methyltetrahydrofuran in organometallic chemistry

“…Breit and coworkers developed a general method for the preparation of primary and secondary alkylmagnesium reagents starting from alkenes (via hydroboration) through the boron-magnesium exchange on alkyl boronates in 2-MeTHF [59]. The authors demonstrated the synthetic usefulness in a wide range of carbon–carbon bond forming reactions, including iron, palladium, and copper-catalyzed cross-couplings.…”