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A. N. Cammidge et al. / Tetrahedron Letters 44 (2003) 6633–6634
methanol to cleave the bound porphyrins which were
isolated (preparative TLC) in yields of 4% (5) and 8%
(6), respectively. It is significant to note that these yields
are higher than those reported for their synthesis on
conventional solid phase.7
In conclusion, surface-functionalised nanoparticles have
been prepared and their utility as solid supports has
been demonstrated. Their reaction sites are uniformly
located at the accessible surface of (selectively) soluble
nanoparticles and they could, therefore, offer advan-
tages over their conventional counterparts in challeng-
ing applications.
Scheme 2. Preparation of surface-functionalised nanoparticles
(see text for details).
References
The utility of the novel polymer supports was investi-
gated using the syntheses of unsymmetrical porphyrins
as model reactions. The synthesis of unsymmetrical
porphyrins is generally a difficult process with typical
yields ranging from 0.5 to 5%.6 The synthesis of unsym-
metrical tetraarylporphyrins on conventional polymer
supports was reported by Leznoff7 using polymer
bound 3- or 4-hydroxybenzaldehyde (Scheme 3) and
this reaction was chosen to permit evaluation of the
nanoparticulate solid support.
1. See for example: Guillere, F.; Orani, D.; Bradley, M.
Chem. Rev. 2000, 100, 2091.
2. Matteucci, C. D.; Caruthers, M. H. J. Am. Chem. Soc.
1981, 103, 3185–3191.
3. (a) Dreja, M.; Puckhout-Hintzen, W.; Tieke, B. Macro-
molecules 1998, 31, 272; (b) Pyrasch, M.; Tieke, B. Colloid
Polym. Sci. 2000, 278, 375.
4. Hesegawa, E.; Eshima, K.; Matshushita, Y. I.; Nishide,
H.; Tsuchida, E. Polymer Bulletin 1995, 14, 31.
5. Polymerisation conditions have been refined to give parti-
cles with a narrow size distribution and average diameter
ca. 100 nm. These results will be reported elsewhere.
6. (a) Little, R. G.; Anton, J. A.; Loach, P. A.; Ibers, J. A. J.
Heterocycl. Chem. 1975, 12, 343–349; (b) Anton, J. A.;
Kwong, J.; Loach, P. A. J. Heterocycl. Chem. 1976, 13,
717–725.
7. Lexnoff, C. C.; Svirskaya, P. I. Angew. Chem., Int. Ed.
Engl. 1978, 17, 947.
8. Beeby, P. J. Tetrahedron Lett. 1977, 38, 3379.
9. Adler, A. D.; Longo, F.; Finarelli, J.; Goldmacher, J.;
Assour, J.; Korsakoff, L. J. Org. Chem. 1967, 32, 476.
The carboxylic acid functionalised support was treated
with oxalyl chloride in CH2Cl2 (DMF initiation)8 and
the resulting polymer-bound acid chloride treated with
either 3- or 4-hydroxybenzaldehyde and pyridine. Com-
plete conversion to the polymer bound aldehyde-ester
was confirmed by IR spectroscopy of the isolated poly-
mer (wCꢀO 1766 and 1705 cm−1). The polymer bound
aldehydes were treated with excess pyrrole and p-tolyl-
benzaldhyde in refluxing propionic acid for 1 h.9 After
washing with CH2Cl2 the resulting polymers (IR 1765
cm−1) were treated with potassium carbonate in
Scheme 3. Polymer supported synthesis of unsymmetrical porphyrins.