Polymer-supported aminopyrimidines

Cox and co-workers reported the cyclization of polymer-supported aminopyrimidines formed by the reduction of nitropyrimidines 73 to produce cyclized pyrimidines 74 after cleavage from the resin <00TL8177>. 

As for the solid support, several polymer-supported amines were tested (Fig. 2). For either the pyrazole and isoxazole synthesis, the best results were given by aniline-functionalized cellulose, which has also the advantage of a relatively low cost. For the 2-aminopyrimidine library, polystyrene-based piperazine and piperidine gave products with a much higher purity compared with other secondary non-cyclic or primary amines, hi both cases, the resins could be reused for up to four times before degradation in their behavior was observed. This reusability could be further enhanced (up to 10 cycles for cellulose-based aniline) when the microwave-assisted protocols were used. 

Fig. 2 Various polymer-supported bases used in the catch-and-release synthesis of pyra-zoles, isoxazoles and 2-aminopyrimidines...

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