Authors: Braden Nelson
Mentors: Nathan S Werner
Insitution: Southern Utah University
The stereocontrolled palladium-catalyzed Suzuki-Miyaura cross-coupling reaction of (E)-2-phenylethenylboronic acid pinacol ester with aryl chlorides to produce (E)-stilbene derivatives was studied. (E)-2-Phenylethenylboronic acid pinacol ester was synthesized by 9-borobicyclo[3.3.1]nonane (9-BBN) catalyzed hydroboration reaction of phenylacetylene with pinacolborane. The reaction conditions of the palladium-catalyzed cross-coupling reaction of this reagent with aryl chlorides were then evaluated to maximize the yield of the cross-coupled product. The maximum yield of (E)-stilbene, 74%, was obtained when the amount of (E)-2-phenylethenylboronic acid pinacol ester was increased from 1.2 to 1.5 equivalents, RuPhos was used as the ligand, K2CO3 was used as the base, and DMF was used as the reaction solvent at 90 °C. Four other aryl chlorides bearing electron-withdrawing and electron-donating substituents in the ortho- and para-positions were found to undergo facile coupling in 91-100% isolated yield.