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The synthesis of biocompatible polymer diclofenac conjugates (PDCs) that have a high drug loading and high degree of control over diclofenac (DCF) release is described.

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The 1,3-dipolar cycloaddition reaction between nitrile imines and resin-bound enamines gives resin-bound pyrazoline intermediates. The piperazine resin functions as a traceless linker and allows these intermediates to be cleaved directly from the resin under mild acid conditions to afford 1,4-diarylpyrazoles. Alternatively they may be chemically modified on the resin prior to elimination from the polymer. The cycloaddition-elimination sequence is regiospecific for the 3,4-disubstituted pyrazole isomer and the products are obtained in good to high yield and in high purity.As part of our drug discovery program we needed to synthesise a range of 1,4-diarylpyrazoles such as pyrazole amide 7 (Scheme 1). A review of the literature indicated that 1,4-diarylpyrazole-3-carboxylates could be prepared via the cycloaddition of an appropriately substituted nitrile imine and phenylacetaldehyde enamines followed by elimination. 1 We sought to apply this chemistry in order to prepare our target compounds and, using solution phase chemistry, the reaction sequence outlined in Scheme 1 proved to be particularly efficient for this purpose. Thus, commercially available ethyl 2-chloroacetoacetate underwent a Japp-Klingemann reaction with the diazonium salt derived from 3-methoxyaniline to