A ONE-POT DOMINO PROTOCOL FOR THE SYNTHESIS OF PYRAZINE AMINE

Abstract

A green and efficient synthetic protocol has been developed for the synthesis of pyrazolo[3,4-b]quinolin-5-ones A and B starting from 1,3-cyclohexanedione, DMFDMA, 3-aminocrotononitrile and the appropriate arylhydrazines. Subsequently an exocyclic double bond has been introduced at C-6 position of A to obtain C, which can serve as a key intermediate for the construction of several heterocyclic hybrids. Further these pyrazolo[3,4-b]quinolin-5-ones C were investigated for their sensitivity against picric acid.

Pyrazoles are five member ring heterocyclic compounds, consisting of a doubly unsaturated five membered ring with two adjacent nitrogen atoms and are also called as azoles. These are aromatic molecules due to their planar conjugated ring structures with six delocalized ?-electrons.1 The term pyrazole was given by Ludwig Knorr in 1883. Being so composed and having pharmacological effects on humans, they are classified as alkaloids, although they are rare in nature. In 1959, the first natural pyrazole, ?-[1-pyrazolyl]alanine was isolated from the seeds of water melons [Citurllus lanatus].2 Literature survey has revealed that till 1930s very little had been done for the synthesis of steroidal pyrazole derivatives. Several pyrazole derivatives have been found to possess significant activities such as 5-?-reductase inhibitor,3 antiproliferative,4 antiparasitic5 and herbicides.6