Res. Chem. Intermed.
, Vol. 27, No. 3, pp. 287–296 (2001)
How radical cations react? — Distonic radical cation
of donor ArCH
, W. LI
, Q.-Y. CHEN
and C.-X. ZHAO
Department of Chemistry, Shanghai Jiaotong University, Shanghai 200240, China
Laboratory of Organo-uorine Chemistry, Shanghai Institute of Organic Chemistry,
Shanghai 200032, China
Received 23 August 2000; accepted 27 November 2000
Abstract—Rate determination and product studies have disclosed that the fragmentation pattern
of radical cations 2-propenyl-1,4-dimethoxybenzene (1
) and 2-propenyl-1,4,5-trimethoxybenzene
) generated in one-electron oxidation of their parent substrates by 4-nitrobenzoyl peroxide (3)
CN is greatly affected by ring-substitution status of the donor molecules. While ring-
benzoloxylation (product 5) predominated in the reaction of dimethoxylated substrate (1), the
oxidation of trimethoxylated donor 2 ended up with distonic radical cation mediated ®,¯-di-4-
nitrobenzoloxylationas the major pathway.
Recent years, more attention has been devoted to establish reaction mechanisms
involving radical cations [1, 2]. New reactions with regioselectivity and stereose-
lectivity have been designed successfully to achieve synthetic strategy  or biolog-
ical studies  on the basis of great understandings about these short-lived species.
The important reaction pathways of radical cations include deprotonation, dimer-
ization, oxidation, reduction, ring-substitution and fragmentation [2, 5, 6]. Ole n
radical cations are of particular interest since they undergo a variety of reactions.
For instance, styrene (including its derivatives with styrene moiety) radical cation
generated by photo-induced electron transfer (PET) is subjected to intensive study
both on product analysis and kinetics. Its addition to precursor ole n to give dim-
mer radical cation and its intermolecular as well as intramolecular additions are
To whom correspondence should be addressed.