# Rhodium-Catalyzed Arene Alkenylation Using Benzoquinone Derivatives as Oxidants

## TL;DR

This paper reports a rhodium-catalyzed method to convert olefins and arenes into alkenyl arenes using benzoquinone derivatives as oxidants.

## Contribution

The study introduces a new catalytic system using benzoquinone derivatives and investigates their impact on reaction rates and selectivity.

## Key findings

- Ortho-benzoquinone derivatives influence reaction selectivity more than para-substituted ones.
- Cyclic voltammetry shows quinone redox potential affects alkenylation rates and selectivity.
- 3,5-di-tert-butyl-ortho-benzoquinone and ortho-chloranil produce significant side products when reacting with ethylene.

## Abstract

The Rh-catalyzed
conversion of olefins and arenes to
alkenyl arenes
using [(η2-C2H4)2Rh­(μ-OPiv)]2 as the catalyst precursor and 12 ortho-
and para-substituted benzoquinone derivatives as the in situ oxidant
is reported. Included are comparative studies of the quinone derivatives
for (1) rate of styrene production from benzene and ethylene, (2)
Markovnikov to anti-Markovnikov selectivity for reactions of benzene
and propylene, and (3) ortho/meta/para selectivity when using tert-butylbenzene as the arene. Cyclic voltammetry was utilized
to measure reduction potentials for each quinone to determine any
possible influence of the quinone redox potential on arene alkenylation
rate and selectivity. While significant differences in selectivity
are observed between ortho-quinone derivatives, such
differences are minimal when para-substituted quinones are utilized.
These results suggest that ortho-benzoquinone derivatives
likely serve as bidentate ligands, which explains the stronger influence
on catalyst activity of ortho-benzoquinone identity
compared to para-benzoquinones. Although ortho-benzoquinones generally give styrene production rates
faster than those of para-benzoquinones, 3,5-di-tert-butyl-ortho-benzoquinone and ortho-chloranil react with ethylene to form bicyclo[2.2.2]­oct-5-ene-2,3-dione
derivatives as a significant side product.