摘要：Monica Oliva,aSerena Pillitteri,aJohannes Schörgenhumer,bRiku SaitocErikV. Van der Eycken,a,dandUpendra K. Sharmaa,e,*

转自：康龙化成

Bromine Radical Release fromNickel-Complex Facilitates the Activation of Alkyl Boronic Acids: A BoronSelective Suzuki-Miyaura Cross Coupling

Monica Oliva,a Serena Pillitteri,a Johannes Schörgenhumer,b Riku Saitoc ErikV. Van der Eycken,a,d and Upendra K. Sharma a,e,*

a.Laboratory forOrganic & Microwave-Assisted Chemistry (LOMAC), Department of Chemistry,University of Leuven (KU Leuven), Celestijnenlaan200F, B-3001 Leuven, Belgium.

b.Department of Chemistry, University of Zurich, Winterthurerstrasse 190,CH-8057

Zurich, Switzerland.

c.Department of Chemistry and Centre for SustainableChemistry, Ghent University Krijgslaan 281(S3), 9000 Ghent, Belgium.

d.Peoples’ Friendship University of Russia (RUDNUniversity), Miklukho-Maklayastreet 6, 117198 Moscow, Russia.

e.Department ofChemistry and Biochemistry, University of Missouri-St. Louis, One UniversityBoulevard, St. Louis, MO 63121, USA.

—Chem.Sci.,2024, 15,17490-17497.

Recommended by Bo Xing_MC4

KEYWORDS: Suzuki-Miyaura (反应类型), photo catalysis (反应类型), Nicatalysis (反应类型),aryl halide (原料),alkyl boronic acid (原料),C(sp3)-C(sp2) (成键类型); BAactivation (其他)

ABSTRACT: Inthis study, without utilizing any exogenous activator or strong oxidants, wesuccessfully employed inactivated and easily accessible alkyl boronic acids(BAs) as coupling partners in a photocatalyzed Suzuki-Miyaurareaction in batch and continuous-flow conditions. Detailed mechanistic studiessuggest aunique BAs activation pathway, via a plausible radical transfer event betweenbromine radical (formed in situ via a photo-induced homolysis of Ni-Br bond)and the empty porbital on the boron atom.Subsequently, the necessity to tune the BA oxidation potential by means ofhydrogen-bonding interaction with solvents or Lewis acid-base type interactions is replacedby a novel halogen radical transfer (XRT) mechanism. The mechanistic hypothesishas been supported by both control experiments and DFT calculations.

PreviousMethods and This Work

Optimizationof Reactions

Selected Scope (selected)

ProposedMechanisms in the Presence of TBABr (on the left) and in the Absenceof TBABr(on the right)

Summary and comments

Prof.Upendra Sharma and co-workershascarried out a novel photocatalyzed Suzuki–Miyaura reaction using both primary andsecondary alkylboronic acidsas radical precursors for the construction of C(sp2)–C(sp3) bonds undermild reaction conditions both in batch and continuous flow. Surprisingly, aunique activation strategy for BAs has been discovered, via a plausibleradical transfer event between a bromine radical (formed in situ via aphoto-induced homolysis of the Ni–Br bond) and the empty p-orbital on the boronatom. With this approach, they have shown a convenient method which canovercome the necessity to match the redox potential of BAs used as radicalprecursors and the employed photocatalyst.

来源：新浪财经