Reaction of 5‐amino‐1‐aryl‐3‐methylpyrazoles with benzylidene derivatives of meldrum's acid: Synthesis and characterization of pyrazolo[3,4‐b]pyridinones

Abstract

A series of dihydropyrazolo[3,4‐b]pyridin‐6‐ones 3 was prepared by cyclization of 5‐amino‐1‐aryl‐3‐methylpyrazoles 1 and Meldrum's acid benzylidene derivatives 2 in nitrobenzene. The structure of 4,5‐dihydropyrazolo[3,4‐b]pyridin‐6‐ones and reaction orientation were determined by nmr measurements.

Diversity‐oriented Multicomponent Heterocyclizations Involving Derivatives of 3(5)‐Aminoisoxazole, Aldehydes and Meldrum's or N,N′‐Dimethylbarbituric Acid

“…It is assumed the both the sequences begin from the formation of the arylidene derivatives of Meldrum's acid 9 , but then there are two alternative pathways for the treatment. Pathway A occurring under heating of the reaction mixture supposes the nucleophilic addition of the CH‐center of 5‐amino‐3‐methylisoxazole 1 to the double bond of compound 9 . Further elimination of acetone and CO 2 results in unstable ketene which cyclizes in the pyridone 5 .…”

An efficient one‐pot synthesis of pyrazolo[3,4‐b]pyridinone derivatives catalyzed by L‐proline

“…Mp: 206–208°C (209–210°C; ref. [8]); IR (potassium bromide): 3142, 3050, 1684, 1595, 1546, 1495, 1385, 1328, 1170, 1085, 1013 cm −1 ; 1 H NMR (DMSO‐ d 6 ): 1.90 (s, 3H, CH 3 ), 2.64 (dd, J 1 = 4.8 Hz, J 2 = 15.6 Hz, 1H, CH 2 ), 3.03 (dd, J 1 = 7.2 Hz, J 2 = 15.6 Hz, 1H, CH 2 ), 4.26 (dd, J 1 = 4.8 Hz, J 2 = 6.8 Hz, 1H, CH), 7.23 (d, J = 8.4 Hz, 2H, ArH), 7.35 (t, J = 7.2 Hz, 1H, ArH), 7.40 (d, J = 8.4 Hz, 2H, ArH), 7.47–7.54 (m, 4H, ArH), 10.57 (s, 1H, NH).…”

“…In particular, condensed pyrazoles are known for various biological activities, e.g ., pyrazolo[3,4‐ b ]pyridines are useful for treatment of a wide variety of stress‐related illnesses, such as depression, Alzheimer's disease, gastrointestinal disease, anorexia nervosa, hemorrhaged stress, drug and alcohol withdrawal symptoms, drug addition, and infertility [5]. Pyrazolo[3,4‐ b ]pyridine derivatives are generally prepared by reaction of 5‐aminopyrazole and substituted α,β‐unsaturated nitriles or benzylidene derivatives of Meldrum's acid in organic solvent ( i.e ., ethanol) using triethylamine as catalyst [6–8], but most of them suffer from drawbacks such as lower yields, and using organic solvent.…”

An efficient synthesis of pyrazolo[3,4‐b]pyrrolo[2,3‐d]pyridines from 5‐aminopyrazoles and cyclic β‐keto ester

“…In our other previous papers [10][11][12], pyrazolo [3,4-b]pyridines were synthesized by Friendlander condensation of 5-aminopyrazole-4-carbaldehyde with various reactive methylene compounds and the heterocyclic compounds with chloroethyl side chain [13]. In literature the pyrazolo [3,4-b]pyridines have been so far obtained by condensation of aminopyrazoles with , -unsaturated compounds [14][15][16][17][18], diethylethoxymethylenemalonate [19,20], active esters [21], cyclic ketones [11,12] and amides [12]. In the present paper, we have used the versatile cyclic -ketoester e.g.…”