Multicomponent Selective and Efficient Synthesis of Spiro[furo[2,3-d]pyrimidine-6,4'-pyrazole] Scaffold Under a Column Chromatography-Free Protocol at Room Temperature.

This new multicomponent tandem Knoevenagel-Michael reaction with further cyclization by the action of N-bromosuccinimide was discovered. The assembly of arylaldehydes, N,N'-dialkylbarbituric acids and 3-methyl-1-phenyl-2-pyrazolin-5-one by the action of NaOAc, and then oxidation of the Knoevenagel-Michael adduct by the N-bromosuccinimide in ethanol without any other additives at ambient temperature, resulted in the selective and efficient formation of the medicinally relevant unsymmetrical 2H-spiro[furo[2,3-d]pyrimidine-6,4'-pyrazole]-2,3',4(2'H,3H)-trione scaffold with three pharmacology active heterocyclic rings in 73-90% yields. This multicomponent reaction is a simple and efficient route to substituted 2H-spiro[furo[2,3-d]pyrimidine-6,4'-pyrazole]-2,3',4(2'H,3H)-triones. This multicomponent method does not require heating, long reaction times, or complex equipment. It is easy to carry out, and the procedure for isolating the final compounds is very simple. Thus, this new multicomponent method is applicable for large-scale processes. All these advantages make this method valuable for the synthesis of new potential biologically active compounds.