Bis(benzofuran-enaminone) hybrid possessing piperazine linker: Versatile precursor for microwave assisted synthesis of bis(pyrido[2',3':3,4]pyrazolo[1,5-a]pyrimidines)

Abstract

We reported herein efficient procedures for the synthesis of new piperazine-linked bis(pyrido[2',3':3,4]pyrazolo[1,5-a]pyrimidines) using bis(benzofuran-enaminone) hybrid as a key intermediate. For this purpose, bis(enaminone) were reacted with a new series of 3-amino-4-(thiophen-2-yl)-1H-pyrazolo[3,4-b]pyridines in pyridine under microwave irradiation at 120 °C for 90 min to afford the target bis(pyrimidines). In a two-steps synthetic route, bis(enaminone) was used to prepare a novel bis(3-amino-1H-pyrazolo[3,4-b]pyridine). Next, the former hybrid was reacted with two equivalents of the appropriate enaminones as well as arylidinemalononitriles in pyridine under microwave irradiation at 120 °C for 2 h to afford the target bis(pyrimidines). Furthermore, a mixture of bis(pyrazolopyridine) reacted with two equivalents of 1,3-diketones and β-ketoesters in glacial acetic acid was microwave irradiated at 130 °C for 90 min to give bis(2,4-disubstituted pyrimidines) and bis(2-substituted pyrimidin-4(1H)-ones), respectively. The structures of the new hybrids were confirmed via considering their elemental analyses as well as their spectral data.

Graphical Abstract

Keywords:

• Cyclocondensation
• 1H-pyrazolo[3,4-b]pyridine
• Michael addition
• piperazine-linked hybrids
• pyrido[2',3':3,4]pyrazolo[1,5-a]pyrimidine