Exploring the Synthesis of Deceptively Simple Biginelli Products through N-CN Bond Cleavage
摘要:
Bronsted-Lowry acid-promoted cleavage of the N-CN bond in 2-cyanoimino-3,4-dihydro-(1H)-pyrimidine is described. Formic acid efficiently activates cyclic N-cyanoguanidines through an O-formylisourea reactive intermediate, leading to chemospecific N-CN bond cleavage of the cyanoimine moiety. This low environmental-load method provides step- and atom-economical access to difficult-to-obtain acid-sensitive Biginelli products in excellent yields.