Silver-catalyzed cascade reactions of 3-cyanochromone with 1,1-enediamines: synthesis of highly functionalized 2-(pyridin-3-yl)-chromeno[2,3-d]pyrimidines†
A novel protocol for the construction of highly functionalized 2-(pyridin-3-yl)-chromeno[2,3-d]pyrimidines (PCPMDs) from 3-cyanochromone with 1,1-enediamines via an unprecedented cascade reaction has been developed by simply refluxing a mixture of 3-cyanochromone 1 and various types of 1,1-enediamines 2 under the catalysis of silver carbonate. As a result, a series of PCPMDs 3 were obtained through a novel cascade reaction involving an amazing electrocyclization mechanism of a cyano group with α,β-unsaturated nitriles. This reaction formation of PCPMDs was accompanied by the formation of four bonds and the cleavage of one bond in one step. This protocol can be used for the synthesis of various pyridin-3-yl-substituted complex pyrimidine derivatives, and it is suitable for combinatorial and parallel syntheses of PCPMD drugs or natural-like products.