Traditional cross-coupling reactions such as the Suzuki and Stille reactions have become a pivotal part of organic synthesis. Direct arylation is being researched as an alternative to traditional cross coupling reactions as it takes less steps to produce the product. Typically, direct arylations are run under an inert atmosphere such as nitrogen or argon. Only recently have accounts surfaced of this transformation under air. Reactions run under an ambient atmosphere are desirable in that they are technically easier to perform and require no special expensive equipment such as a Schlenk line or glove box. The goal of this research was to better understand the relationship between the structure of biaryl phosphine (Buchwald) ligands and product yield in an under air direct arylation reaction. In order to rapidly screen results, GC yields of the direct arylation product were obtained. Standard solutions were created using a GC-MS to make calibration curves for each analyte. These standard solutions included concentrations of 4-bromotoluene, the cross coupling product, a homo-coupling byproduct, and tetradecane (an internal standard). Results (measured on the GC-MS) show that phosphine ligands with either cyclohexyl groups or bis-3,5-bis(trifluoromethyl) phenyl attached to the phosphorus increase reactivity. Reactivity also increased when ligands with meta NMe2, Oi-Pr, or OMe groups on the lower benzene ring.

Relationship between biaryl ligand structure and reactivity in under-air direct arylation

253rd National Meeting (2017)

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