Linear-Selective Hydroarylation of Unactivated Terminal and Internal Olefins with Trifluoromethyl-Substituted Arenes

We report a series of hydroarylations
of unactivated olefins with
trifluoromethyl-substituted arenes that occur with high selectivity
for the linear product without directing groups on the arene. We also
show that hydroarylations occur with internal, acyclic
olefins to yield linear alkylarene products. Experimental mechanistic
data provide evidence for reversible formation of an alkyl­nickel–aryl
intermediate and rate-determining reductive elimination to form the
carbon–carbon bond. Labeling studies show that formation of
terminal alkylarenes from internal alkenes occurs by initial establishment
of an equilibrating mixture of alkene isomers, followed by addition
of the arene to the terminal alkene. Computational (DFT) studies imply
that the aryl C–H bond transfers to a coordinated alkene without
oxidative addition and support the conclusion from experiment that
reductive elimination is rate-determining and forms the anti-Markovnikov
product. The reactions are inverse order in α-olefin; thus the
catalytic reaction occurs, in part, because isomerization creates
a low concentration of the reactant α-olefin.