Issue 6, 2011

Synthesis of 3- and 5-formyl-4-phenyl-1H-pyrazoles: promising head units for the generation of asymmetric imineligands and mixed metal polynuclear complexes

Abstract

Two synthetic methodologies are reported for the generation of 4-phenyl-1H-pyrazoles substituted at the 3- and/or 5-positions. Functionalisation of the 4-position of dimethyl-4-iodo-1-(tetrahydropyran-2-yl)-3,5-pyrazolecarboxylate (10) to produce dimethyl-4-phenyl-1-(tetrahydropyran-2-yl)-3,5-pyrazolecarboxylate (14) was achieved by a C–C Suzuki–Miyaura cross coupling reaction in water. However, low yields for this reaction led us to develop a second methodology wherein functionalisation of N-(tetrahydropyran-2-yl)-4-phenylpyrazole (18), synthesised from inexpensive phenylacetic acid, with formyl or hydroxymethyl groups was achieved by lithiation methods. The resulting monoaldehydes, 4-phenyl-5-pyrazole carbaldehyde (20) and 5-formyl-3-(2′-tetrahydropyranyloxymethyl)-4-phenyl-1-(tetrahydropyran-2-yl)pyrazole (28), should facilitate access to new, asymmetric, imine ligands based on a 4-phenyl-1H-pyrazole moiety. This was proven by the successful synthesis of the heterometallic tetranuclear complex [FeII(NiIIL2)3](BF4)2·solvents. Likewise, the alcohol isolated en route to 28, N-(tetrahydropyran-2-yl)-5-(hydroxymethyl)-4-phenylpyrazole (24), should facilitate access to new, asymmetric, amine ligands.

Graphical abstract: Synthesis of 3- and 5-formyl-4-phenyl-1H-pyrazoles: promising head units for the generation of asymmetric imine ligands and mixed metal polynuclear complexes

Supplementary files

Article information

Article type
Paper
Submitted
11 Oct 2010
Accepted
16 Nov 2010
First published
16 Dec 2010

New J. Chem., 2011,35, 1242-1253

Synthesis of 3- and 5-formyl-4-phenyl-1H-pyrazoles: promising head units for the generation of asymmetric imine ligands and mixed metal polynuclear complexes

J. Olguín and S. Brooker, New J. Chem., 2011, 35, 1242 DOI: 10.1039/C0NJ00774A

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