Green Route for Precursors for Suzuki Coupling Recognized

Washington, DC (June 24)-Robert E. Maleczka Jr. and Milton R. Smith III, professors of the Department of Chemistry at Michigan State University, were recognized by the Environmental Protection Agency’s Presidential Green Chemistry Challenge Awards for designing a catalytic reaction to synthesize precursors for the Suzuki-coupling reaction.

The Presidential Green Chemistry Challenge Awards were launched in 1995. They are given annually to recognize chemical technologies that incorporate the principles of green chemistry into chemical design, manufacture, and use, and that have been or can be used by industry in achieving pollution-prevention goals.

The Suzuki reaction is the palladium-catalyzed coupling of aryl halides and arylboronic acids. The reaction is used in the synthesis of active pharmaceutical ingredients (1). The professors initially began collaborating to find a halogen-free way to prepare organoboron compounds, specifically the aryl and heteroaryl boronic esters, which are key building blocks for Suzuki couplings (2).

They developed an approach that uses an iridium catalyst to synthesize the boronic ester precursors without solvent and with only hydrogen as a coproduct. The catalytic carbon–hydrogen activation/borylation allows the direct construction of aryl boronic esters from hydrocarbon feedstocks in a single step, without an aryl intermediate, without certain limitations of aromatic-substitution chemistry, and without certain functional-group restrictions. The transformations using the iridium catalysts are tolerant of various functional groups (i.e., alkyl, halo, carboxy, alkoxy, and amino groups). Also, given its mildness, the borylation chemistry can be readily combined in situ with subsequent chemical reactions (2).

Michigan State University has licensed the technology to BoroPharm (Novi, MI). BoroPharm is a manufacturer of boron intermediates and related products (2).

References
1. N. Miyaura and A. Suzuki, “Palladium-Catalyzed Cross-Coupling Reactions of Organoboron Compounds,” Chem. Rev. 95 (7) 2457–2483 (1995).

2. Environmental Protection Agency, “The Presidential Green Chemistry Challenge Awards Program: Summary of 2008 Award Entries and Recipients,” (Washington, DC, 2008).