A Study of Polarization and Directing Effects of Unsymmetrical Alkynes Using Regioselective Pd-Catalyzed Bromoallylation
2020
Abstract
Herein is disclosed the first comprehensive study of factors that affect the regioselectivity of PdBr2(PhCN)(2)-catalyzed bromoallylation of unsymmetrically substituted internal alkynes. The study was performed on a wide array of electronically and structurally diverse alkynes with aryl-aryl, aryl-ferrocenyl, and aryl-alkyl substitutions.
The regioselective formation of bromoallylation products was mostly driven by the polarization of the triple bond in aryl-aryl and aryl-ferrocenyl-substituted ethynes. On the other hand, directing effect, which arises from the presence of a directing group in the side-chain of aryl-alkyl-substituted alkynes, was the dominating factor that determined the regioselectivity of these reactions.