ORGANIC
LETTERS
2002
Vol. 4, No. 11
1975-1977
ROMPgel-Supported Triphenylphosphine
with Potential Application in Parallel
Synthesis
Erik A° rstad, Anthony G. M. Barrett,* Brian T. Hopkins, and Johannes Ko1bberling
Department of Chemistry, Imperial College of Science, Technology and Medicine,
London SW7 2AY, United Kingdom
Received April 12, 2002
ABSTRACT
ROMPgel-supported triphenylphosphine was synthesized in three steps (67%) from norbornadiene, 4-bromoiodobenzene, and chlorodiphenyl-
phosphine. The supported reagent has a high loading (2.5 mmol/g) and favorable swelling properties in organic solvents. It has been utilized
for the conversion of alcohols to halides, the reduction of ozonides, and the isomerization of r,â-acetylenic esters and in the Staudinger
reaction. In general, filtration of the resin from the reaction mixtures and evaporation gave the corresponding products in high yield and
purity.
Immobilized reagents, catalysts, and scavenger reagents
combine the advantages of simple purification, in that only
filtration and washing are required to remove large excesses
of reagents, with the ease of reaction monitoring associated
with classical solution phase methodologies. It is therefore
not surprising that the use of solid-supported reagents has
become the subject of considerable emphasis within the past
few years. A range of such reagents has been developed, of
which most are either based on polystyrene beads or
inorganic supports.1 Recent efforts have improved their
loading and physical properties, resulting in highly versatile
reagents. Nonetheless, there is need to simplify the elabora-
tion and costs of solid-supported reagents and to further
improve their properties. In these terms, the use of polymers
derived from ring-opening metathesis (ROM) has the ad-
vantage that ruthenium carbenes can convert readily available
and highly functionalized monomers to well-defined sup-
ported reagents (ROMPgels).2 The resulting polymers have
high loadings and undergo significant swelling in various
solvents. A range of ROMPgel-supported reagents have been
prepared and used in parallel synthesis.3
Due to the many transformations involving triphenylphos-
phine and the difficulties encountered in subsequent workup,
this reagent was among the first to be made available on a
polymer support.4 To further explore the scope of the ROMP
methodology, we herein report the synthesis and utilization
of ROMPgel-supported triphenylphosphine 4.
4-Bromoiodobenzene (1) was coupled to norbornadiene
via a palladium-catalyzed exo-hydroarylation reaction to
afford the bromide 2 (80%). Bromide 2 was allowed to react
with butyllithium and chlorodiphenylphosphine to produce
the phosphine monomer 3 in 92% yield (Scheme 1).
(2) (a) Buchmeiser, M. R. Chem. ReV. 2000, 100, 1565. (b) Bielawski,
C. W.; Grubbs, R. H. Angew. Chem., Int. Ed. 2000, 39, 2903.
(3) (a) Barrett, A. G. M.; Cramp, S. M.; Roberts, R. S.; Zecri, F. J. Org.
Lett. 1999, 1, 579. (b) Barrett, A. G. M.; Cramp, S. M.; Hennessy, A. J.;
Procopiou, P. A.; Roberts, R. S. Org. Lett. 2001, 3, 271. (c) Arnauld, T.;
Barrett, A. G. M.; Seifried, R. Tetrahedron Lett. 2001, 42, 7899. (d) Arnauld,
T.; Barrett, A. G. M.; Cramp, S. M.; Roberts, R. S.; Zecri, F. J. Org. Lett.
2000, 2, 2663.
(1) (a) Ley, S. V.; Baxendale, I. R.; Bream, R. N.; Jackson, P. S.; Leach,
A. G.; Longbottom, D. A.; Nesi, M.; Scott, J. S.; Storer, R. I.; Taylor, S.
J. J. Chem. Soc., Perkin Trans. 1 2000, 23, 3815. (b) Kirschning, A.;
Monenschein, H.; Wittenberg, R. Angew. Chem., Int. Ed. 2001, 40, 651.
(4) McKinley, S. V.; Rakshys, J. W. J. Chem. Soc., Chem. Commun.
1972, 134. For a recent example of the use of this reagent, see: Lizarzaburu,
M. E.; Shuttleworth, S. J. Tetrahedron Lett. 2002, 43, 2157 and references
therein.
10.1021/ol026008q CCC: $22.00 © 2002 American Chemical Society
Published on Web 05/08/2002