One-Pot Synthesis of 2,3-Disubstituted Pyrimido[1,2-b]indazole Skeletons from 3-Aminoindazole and Two Distinct Amino Acids

An effective synthesis for 2,3-disubstituted pyrimido[1,2-b]indazole from 3-aminoindazole and two amino acids was developed. This strategy has been demonstrated with a variety of 3-aminoindazole and amino acids, and it has been successfully scaled up to gram-scale synthesis, highlighting the practicality and application value of the protocol. Furthermore, the utilization of amino acids not only reduces the formation of byproducts but also renders the reaction more environmentally friendly. Mechanistic studies revealed that I₂ promoted the decarboxylation of amino acids and the subsequent oxidative cyclization process.