Electrocatalytic Multicomponent Transformation of Aldehyde, 5-Amino-3-methyl-1-phenylpyrazole and Dimedone: An Efficient Protocol for Substituted Pyrazolo[3,4-b]quinolines

A convenient, rapid and electrochemical one-pot protocol was developed successfully for the preparation of pyrazolo[3,4-b]-quinoline derivatives. The reaction is carried out in a 25 mL three neck flask equipped with graphite electrode as anode and iron electrode as cathode (electrode area of 1 cm(2)) with sodium bromide as supporting electrolyte at room temperature in ethanol. Fourteen pyrazolo-[3,4-b]-quinoline derivatives were synthesized by use of various aldehyde (including aryl aldehydes and aliphatic aldehydes), dimedone and 5-amino-3-methyl-1-phenylpyrazole as substrates in good yields (76-86 %) with a constant current of 30 mA after 0.14 F/mol of electricity passed. All aimed products were characterized by IR, H-1 NMR and HRMS. Notably, the presented method features ecologically sound, simple experimental procedure and good yields.