ORGANIC
LETTERS
2001
Vol. 3, No. 6
855-857
A New Supported Reagent for the
Photochemical Generation of Radicals
in Solution
Lidia De Luca, Giampaolo Giacomelli,* Giancarlo Porcu, and Maurizio Taddei
Dipartimento di Chimica, UniVersita` degli Studi di Sassari, Via Vienna 2,
I-07100 Sassari, Italy
Received December 21, 2000
ABSTRACT
A new polymer-supported radical source was developed by loading an N-hydroxy thiazole 2(3)-thione on a Wang resin. This new supported
reagent can be employed for a solid-phase version of the Hunsdiecker reaction or to liberate free alkoxy radicals, in a variant of the “catch
and release” technique, under very mild conditions (irradiation with a discharge lamp) and simplifying the purification procedure.
The current development of new methods for the synthesis
of organic molecules on a solid support has led to a renewed
interest in a complementary technique in which a polymer-
based reagent is employed to generate new products in
solution. Polymer-supported reagents have been in use for
the past 40 years. However, they are receiving considerable
interest recently with the growth of high throughput solution-
phase synthesis.1 Parallel syntheses in solution using solid-
supported reagents may be attractive because the reactions
are often clean, it is possible to monitor the conversion using
standard analytical techniques, and the final workup involves
simple filtration and evaporation of the solvent. Polymer-
supported reagents have been used in oxidations,2 reductions,3
halogenations,4 and coupling reactions5 and as scavengers6
or ligands.7 Supported reagents for the generation of radicals
in solution may be very useful in the synthesis of libraries
in solution. Many reports describe a radical precursor
attached to a resin8 so that the radical acceptor or the Bu3-
SnH, used in the cyclization reaction, can be washed off at
the end of the reaction. Alternatively, supported triorganotin
hydrides have been developed to avoid the problem of
separation of the stannylated byproducts present in solution.9
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J. Chem. Soc., Perkin Trans. 1 1999, 2, 107. Thompson, L. A. Curr. Opin.
Chem. Biol. 2000, 4, 324-337. Hodges, J. C. Synlett 2000, 152-158.
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M.; Poon, S. Med. Chem. ReV. 1999, 2, 97-148. Shuttleworth, S. J.; Allin,
S. M.; Wilson, R. D.; Nasturica, D. Synthesis 2000, 1035-1074. Ley, S.
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10.1021/ol007032b CCC: $20.00 © 2001 American Chemical Society
Published on Web 02/17/2001