Zinc‐Catalyzed Borylation of Primary, Secondary and Tertiary Alkyl Halides with Alkoxy Diboron Reagents at Room Temperature

Abstract

A new catalytic system based on a Zn(II) NHC precursor has been developed for the cross-coupling reaction of alkyl halides with diboron reagents, which represents a novel use of a Group XII catalyst for CX borylation. This approach gives borylations of unactivated primary, secondary, and tertiary alkyl halides at room temperature to furnish alkyl boronates, with good functional-group compatibility, under mild conditions. Preliminary mechanistic investigations demonstrated that this borylation reaction seems to involve one-electron processes.

Catalytic Borylation using an Air‐Stable Zinc Boryl Reagent: Systematic Access to Elusive Acylboranes

“…[21] This finding is in agreement with the fact that simple and heterogeneous forms of palladium (see Table S1), as well as palladium black generated in situ, are barely active.N evertheless,t he role of palladium nanoparticles cannot be completely ruled out at this stage.A radical pathway related to that previously proposed in zinccatalyzed borylation reactions seems unlikely, [22] since little [a] Reaction conditions: 3 (0.022 mmol), 7 (0.040 mmol), [Pd{P(o-Tol) 3 } 2 Cl 2 ](3mol %), THF (0.5 mL), 80 8 8C, 2h.Yields were calculated by 1 HNMR spectroscopy using an internals tandard. Carbon disulfide and phosphine quenching experiments suggest that ah omogeneous palladium species is the active catalyst (see the Supporting Information).…”

Copper(i)-catalyzed carbon–halogen bond-selective boryl substitution of alkyl halides bearing terminal alkene moieties

“…3 Following on from these early publications, several other methods have been reported for the boryl substitution of alkyl halides using a variety of different transition metal catalysts (e.g., Ni, Pd, Zn and Fe) (Scheme 1a). [4][5][6][7][8] Alkyl halides bearing a terminal alkene moieties can be converted to a variety of borylation products through three different reaction pathways, including the hydroboration of the terminal C=C double bond, 9 borylative cyclization 10 and boryl substitution of the C-X bond (Scheme 1b). Conventional hydroboration reactions allow for the selective reaction of an organoborane compound with a C=C double bond to give the corresponding alkylboron compounds containing a carbon-halogen bond.…”

Harnessing Alkyl Amines as Electrophiles for Nickel-Catalyzed Cross Couplings via C–N Bond Activation

“…5 Following pioneering developments with alkyl halides, 6 pseudohalides, 6n, 7 and organometallic nucleophiles, 8 dual photoredox/nickel catalysis has enabled use of oxalates, 9 carboxylic acids, 10 1,4-dihydropyridines, 11 organoboronates, 12 and organosilicates. 13 Redox-active esters are also potent alkylating agents without need for a photocatalyst.…”

“…Both monometallic “transmetallation-first” and radical chain bimetallic SET oxidative addition are known; we cannot currently distinguish these possibilities. 6w, 26 …”