Transmetalation from boronic esters to arylpalladium complexes without prior hydrolysis – mechanistic studies and preparative applications in the anhydrous, Suzuki-Miyaura cross-coupling reaction

Delaney, Connor P

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https://hdl.handle.net/2142/109332 Copy

Description

Title

Transmetalation from boronic esters to arylpalladium complexes without prior hydrolysis – mechanistic studies and preparative applications in the anhydrous, Suzuki-Miyaura cross-coupling reaction

Author(s)

Delaney, Connor P

Issue Date

2020-09-08

Director of Research (if dissertation) or Advisor (if thesis)

Denmark, Scott E

Doctoral Committee Chair(s)

Denmark, Scott E

Committee Member(s)

• Burke, Martin D.
• Murphy, Catherine J.
• Hergenrother, Paul J.

Department of Study

Chemistry

Discipline

Chemistry

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• cross-coupling
• Suzuki-Miyaura
• transmetalation
• boronic ester
• palladium
• mechanism

Abstract

The formation of C–C bonds is a foundational aspect of organic chemistry, and the development of transition-metal catalyzed, cross-coupling reactions has fundamentally changed the way chemists think about C–C bond formation. Within the class of transition-metal catalyzed, cross coupling reactions, the Suzuki-Miyaura reaction has emerged as the most popular method because of the relative non-toxicity of organoboron derivatives, the extensive reaction scope that has been demonstrated with the method, and the inertness of organoboron reagents towards other functional groups. Considering the importance of the Suzuki-Miyaura reaction in a variety of fields, the mechanism by which the reaction occurs is of considerable interest, The work described in this dissertation has focused on further developing our mechanistic understanding of Suzuki-Miyaura reaction, and leveraging new mechanistic insights to develop powerful cross-coupling methods. For the first time, pre-transmetalation intermediates incorporating boronic esters have been characterized, proving the competency of boronic esters to undergo transmetalation without prior hydrolysis. Boronic ester structure was found to have a significant impact on both pretransmetalation intermediate speciation and the rate of arene transfer; several boronic esters examined were found to undergo transmetalation over 20 times faster than the corresponding boronic acid. To harness this increase in the rate of transmetalation, an anhydrous, homogeneous cross-coupling method was developed to cross-couple boronic esters without hydrolysis to the boronic acid. Whereas most boronates are insoluble in organic solvent, boronates derived from potassium trimethylsilanolate (TMSOK) and neopentyl boronic esters are freely soluble in ethereal solvents, allowing anyhydrous cross-coupling without interference from mass-transfer effects. Finally, the mechanism of the TMSOK-promoted Suzuki-Miyaura reaction was investigated, revealing surprising insights into the mechanism of transmetalation from organic-soluble boronates in the Suzuki-Miyaura reaction.

Graduation Semester

2020-12

Type of Resource

Thesis

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http://hdl.handle.net/2142/109332

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Copyright 2020 Connor Delaney

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