||I U P A C
Organizations & People
Appl. Chem., Vol. 72, No. 7, pp. 1327-1334,
Special Topic Issue on Green Chemistry
Free radicals in synthesis. Clean reagents affording oxidative or
John A. Murphy
Department of Pure and Applied Chemistry, University
295 Cathedral Street, Glasgow, G1 1XL, UK
Abstract: Neurotoxic organotin reagents currently play a key
role in radical chemistry. As a result, this is an important area for
development of new clean replacement reactions. The pharmaceutical industry
in particular has had to avoid use of radical methodology for the formation
of carbon_carbon bonds for this reason. With the current dawn in green
chemistry, a host of new clean radical methods is beginning to flourish.
Our aim has been to develop new nontoxic methodology for carbon_carbon
bond formation by radical chemistry, which would provide either reductive
termination (giving a hydrogen atom to the ultimate radical, as happens
with tributyltin hydride), or oxidative functionalization, installing
a useful polar group at the site of the ultimate radical. Two methods
for effecting radical reactions in an environmentally friendly way are
presented: (i) The tetrathiafulvalene (TTF)-mediated radical-polar crossover
reaction converts arenediazonium salts to aryl radicals, which have
sufficient lifetime to cyclize onto alkenesthe resulting alkyl
radicals couple with TTF+ to afford sulfonium salts
which, in turn, undergo solvolysis to alcohols, ethers or amides. The
method provides the key step in a synthesis of (±)-aspidospermidine.
(ii) Hypophosphite salts and hypophosphorous acid, on the other hand,
form C_C bonds with reductive termination. These economical reagents
afford radicals efficiently, starting from aryl iodides, alkyl bromides,
and alkyl iodides, and give very easy separation of products from by-products.
Back to Contents for access to full
Page last modified 5 November 2000.
Copyright ©2000 International Union of Pure and Applied Chemistry.
Questions or comments about IUPAC, please contact, the Secretariat.
Questions regarding the website, please contact web