Polyphosphoric acid-promoted synthesis of coumarins lacking substituents at positions 3 and 4

Exploration of 3,4-unsubstituted coumarins as thioredoxin reductase 1 inhibitors for cancer therapy

“…At first, to obtain the different coumarin analogues 2a,2b and 3a,3d , the approach based on modified Perkin condensation of salicylaldehyde and acetic anhydride promoted by polyphosphoric acid (PPA) was employed (Scheme 1, Method A). 16 The final products with Br or NO 2 as substituents were obtained in moderate yields.…”

“…To broaden and systemise the scope of coumarins, classical and/or modified recently published synthetic methodologies were used. However, known methods for the synthesis of the desired 3,4-unsubstituted analogues are very limited, and it can be performed by Perkin condensation 16 and organocatalytic procedures 17 using salicylaldehyde or phenol 18 derivatives as starting materials. At first, to obtain the different coumarin analogues 2a,2b and 3a,3d , the approach based on modified Perkin condensation of salicylaldehyde and acetic anhydride promoted by polyphosphoric acid (PPA) was employed (Scheme 1, Method A).…”

“…Compounds 2b and 3a,d were prepared according to the unmodified literature procedure in the presence of PPA and were assigned to synthetic Method A. 16 Compounds 2a,b and 2d were synthesized according to the unmodified literature procedure in the presence of PPA and were assigned to synthetic Method B. 17 Compound 2c was prepared according to the literature procedure.…”

Identification of Ureidocoumarin-Based Selective Discoidin Domain Receptor 1 (DDR1) Inhibitors via Drug Repurposing Approach, Biological Evaluation, and In Silico Studies

“…The target ureidocoumarins 3a–p and 4a–c were synthesized using 6-aminocoumarin 2 as the main component, as shown in Scheme 1 . First, 2-hydroxy-5-nitrobenzaldehyde was converted to 6-nitrocoumarin 1 [ 33 ] by reacting it with acetic anhydride in a mixture of polyphosphoric acid (PPA) and dimethylformamide (DMF) at 145 °C. Then, 1 was reduced to the corresponding amine 2 in good yield by either iron powder in a solution of AcOH:EtOH:water [ 34 ] or SnCl 2 dihydrate in ethanol [ 35 ].…”

A facile synthesis of bridged polycyclic compounds consisting of chromeno-oxazocine- quinolin skeletons: Eight-Membered-Ring constructions via tandem dinucleophilic addition of 4- hydroxycoumarin to 1,10-phenanthrolin-1-ium Salts

“…Next, coumarin is one of the key core segments in active pharmaceutical ingredients, bioactive natural and synthetic products [37][38][39]. Compounds having the coumarin scaffold have been illustrated to possess a broad range of biological activities including anti-oxidant [40][41], anti-in ammatory [42][43],…”