101740
5-Chloro-3-methyl-1-phenylpyrazole-4-carboxaldehyde
5-Chloro-3-methyl-1-phenylpyrazolecarboxaldehyde 1 is a white crystalline solid (mp 149°C) which is thermally stable. The chloro function of 1 is activated towards nucleophilic substitution. 1 has been used as the starting material for the corresponding thiolates 2 (1), azides 3 (2) and amines 4 (3) which can be converted to ligands for transition metal complexes, or condensed heterocycles. The azides 3 give a number of interesting rearrangements(4). Condensation of 1 with bisnucleophiles gives fused heterocycles, such as thienopyrazoles (1) or fluorescent dyes (5). 1 was used in tandem processes to introduce an unsaturated chain by nucleophilic substitution, followed by conversion of the remaining aldehyde function into a 1,3-dipole or heterodiene, followed by an intramolecular cycloaddition to afford polycyclic heterocycles(6). 1 has also been used in the synthesis of meso-substituted heterocyclic porphyrins(7).
References
(1) J. Becher, P.H. Olesen, N. A. Knudsen and H. Toftlund, Sulfur Lett. 1986,4 ,175
(2) P. Molina, A. Arques, M. V. Vinader, J. Becher, K. Brondum, J. Org. Chem. 1988,53 , 4654
(3) J. Becher, K. Pluta, N. Krake, K. Brondum, N. J. Christensen, M. V. Vinader, Synthesis, 1989, 530
(4) G. Labbé, L. Dyall, K. Meersman and W. Dehaen, J. Chem. Soc., Perkin Trans. 1994,1, 2401 and references cited therein
(5) U. V. Gokhale, S. Sehradi, Dyes Pigm. 1987, 8 , 157
(6) E. Ceulemans, S. Emmers, M. Voets and W. Dehaen, Synlett, 1997 , 1155 and references cited therein
(7) M. Bruix, J. Elguero, W. Meutermans, J. Chem. Res. (S) 1992,370
