Silver-catalyzed decarboxylative cyclization for the synthesis of substituted pyrazoles from 1,2-diaza-1,3-dienes and α-keto acids

A silver-catalyzed decarboxylative cyclization process has been developed for the synthesis of substituted pyrazoles from the readily available 1,2-diaza-1,3-dienes and alpha-keto acids. Under the optimized conditions, a series of multisubstituted pyrazoles were well prepared in moderate to good yields. In addition, the synthetic utility of this protocol has been demonstrated by synthesizing analogs of FDA approved drugs such as anti-inflammatory drug, lonazolac and antiobesity drug, rimonabant.