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Pyrazolo[3,4-b]pyridines (4) and (5) have been obtained by the condensation of 3-(alkyl/aryl)-5-amino-l-phenyl-lH-pyrazole-4-carboxaldehydes (3) with active methylene compounds viz: diethyl malonate and malononitrile. The discovery that pyrazolo[3,4-b]pyridines are involved in various pharmacological applications"22 as good vasodialators, hypotensive, hypoglycemic, antiinflammatory, analgesic and antipyretic agents have promoted a great current interest in facile and general routes to these molecules in synthetically useful yields. The earlier method of synthesis of such systems involve the c y~l i s a t i o n~'~ of 4-substituted pyrazolinones with NH40Ac and PPA. W e now report a novel synthetic route to the synthesis of pyrazolo[3,4-b]pyridines which involve annulation of a pyridine ring onto the preformed pyrazole ring. The reaction involves the condensation of 3-(alkyl/aryl)-5-amino-l-phenyl-1H-pyrazole-4-carboxal~ehydes (3) with active methylene compounds viz: diethyl malonate and malononitrile (Scheme-1).o-Aminoaldehyde derivatives are the key intermediates for the synthesis of various biologically active heterocy~les6~The essential intermediate 3-(alkyVaryl)-5-amino-1-phenyl-lH-pyrazole-4-carboxaldehydes (3) has been prepared as follows:

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Synthesis of 1,3-Diaryl-7,7-diethyl-5-methyl-4-oxo-2-thioxo-1,2,3,4tetrahydro-7H-pyrano(2,3-d)pyrimidines.-The compounds (IIIa) and (Vb) display significant activity against Staphylococcus aureus, (IIId) and (Vd) against Escherichia coli and the derivatives (IIIc), (Va), (Vd) and (Ve) inhibit the growth of Aspergillus niger. -(AHLUWALIA, V. K.; BATLA, R.; KHURANA, A.; KUMAR, R.; Indian J.