Utility of complementary molecular reactivity and molecular recognition (CMR/R) technology and polymer-supported reagents in the solution-phase synthesis of heterocyclic carboxamides

The use of our recently reported chemical library purification strategy in the development of a herbicidal lead, N-(3-benzoylphenyl)-3-(1,1-dimethylethyl)-1-methyl-1H-pyrazole-5-carboxamide (3), is described. The approach applying fundamental properties of complementary molecular reactivity and molecular recognition (CMR/R) as the basis for a general purification strategy was utilized. Polymeric reagents were used in the synthesis to generate reactive species involved in product formation, and complementary molecular reactivity/molecular recognition polymer 8 (CMR/R polymer 8) was used in the solution-phase syntheses of building blocks, primary libraries, and lead refinement libraries. An extension of the CMR/R methodology was applied, utilizing a sequestration enabling reagent (SER), transforming a reactant into an electrophilic species sequestrable by CMR/R polymer 8. This library purification strategy enabled rapid lead generation and lead refinement to afford herbicide 27o. The CMR/R solid-phase purification technique enabled a simple, general, and powerful protocol, eliminating the usual tedious and time-consuming methods required for solution-phase product purification. The result was the synthesis of hundreds of compounds, prepared in a relatively short time, leading to a compound with a 4-fold improvement in herbicidal activity over the initial lead.