Kullampalayam Krishnasamy Sivakumar et al synthesized 28 some mannich base of 5-methyl-[(2-oxo-2H-chromen-3-yl) carbonyl]-2,4-dihydro-3H-pyrazol-3-one (Fig. 20) by using conventional and non conventional (microwave) techniques. Ethyl 2-oxo-2H-chromene-3-carboxylate was prepared by cyclization of salicylaldehyde with diethylmalonate in presence of catalytic amount of piperidine. Reaction of this ester compound with hydrazine hydrate in ethanol formed 2-oxo-2H-chromene-3-carbohydrazide.
A facile and efficient approach for the synthesis of title compounds has been developed. A series of titled compounds, i.e., coumarinyl triazolothiadiazoles have been synthesized using appropriate synthetic procedures, In step 1,ethyl ester of coumarin (1) has been synthesized from salicylaldehyde and diethyl malonate by Knoevenagel condensation. In step 2, the formed ethyl ester of coumarin was hydrazinolysed to give hydrazides (2) by treating with hydrazine hydrate, which reacted with carbon disulphide and potassium hydroxide in ethanol to yield potassium dithiocarbazinate (3), which later cyclized to form 1, 2, 4-triazole (4) by reacting with hydrazine hydrate. The resulted triazole moiety further converted to triazolothiadiazoles by the condensation with different aromatic acids in the presence of phosphorous oxy chloride.
Coumarin from salicylaldehyde | Salicylaldehyde
An equimolar mixture of 3-(4-amino-5-sulfonyl-4H-1, 2, 4-triazol-3-yl)- 2H-chromene-2-one  (0.001M) and substituted aromatic acids (0.001M) in dry Phosphorous oxy chloride (15ml) was refluxed for 10-12 hrs. Completion of the reaction was judged by TLC. The reaction mixture was cooled to room temperature and then gradually poured onto crushed ice with constant stirring. The solid thus separated was filtered, washed with water and recrystalized from ethanol.
Room Temperature One-Pot Green Synthesis of Coumarin …
2-oxo-2H-chromene-3-carbohydrazide (2) was added to KOH (0.015mole) solution which is dissolved in absolute ethanol in cool condition. To this, carbon disulfide (0.015M) was added in small portions with constant stirring. The reaction was agitated continuously for a period of 32-35 hrs and product was isolated from diethyl ether. The precipitated potassium dithiocarbazinate was collected by filtration. The precipitate was further washed with anhydrous ether and dried.
Reactions of salicylaldehyde | Salicylaldehyde
A mixture of N (3-chloro-4-methoxy) phenyl malon anilic acid (0.001mole ; 1a) and (0.001mole ;5a-5l) in equi molar quantity (1:1), with few drops of pyridine, the reaction mixture was heated for 4-hours in an oil-bath at 104-110OC, the mixture was first melted and then soon set to a solid, cooling, then the product was digested with the saturated solution of Sodium bicarbonate, washed with water, the azo-schiff’s base was removed by the extraction with hot ethanol (15 ml), the filtrate was concentrated and cooling, the obtained product was identified as substituted azo-schiff’s base (7a – 7l), the residue was recrystallized from hot ethanol several times and identified to be substituted azo-coumarin (6a-6l).
Pechmann Condensation - Organic chemistry
A mixture of ethyl-2-oxo-2H-chromene-3-carboxylate  (0.01 mole, 1.9 gm) and hydrazine hydrate (0.02 mol, 2ml) in absolute ethanol was refluxed for 5-6 hr. Completion of the reaction was judged by TLC. After cooling, the reaction mixture was added to the cool water. The solid, thus separated, was collected by filtration, dried and recrystalized from ethanol.
Synthesis and evaluation of 11C-labeled coumarin …
Coumarins comprise a very large class of compounds found throughout the plant kingdom 4-6. They are found at high levels in some essential oils, particularly cinnamon bark oil (7,000 ppm), cassia leaf oil (up to 87,300 ppm) and lavender oil. Coumarin is also found in fruits (e.g. bilberry, cloudberry), green tea and other foods such as chicory 7. Most coumarins occur in higher plants, with the richest sources being the Rutaceae and Umbelliferae. Although distributed throughout all parts of the plant, the coumarins occur at the highest levels in the fruits, followed by the roots, stems and leaves. Environmental conditions and seasonal changes can influence the occurrence in diverse parts of the plant 8. Recently six new minor coumarins have been isolated from the fruits and the stem bark of Calophyllum dispar (Clusiaceae). The genus Calophyllum, which comprises 200 species, is widely distributed in the tropical rain forest where several species are used in folk medicine 9. Although most of the natural coumarins in existence have been isolated from the higher plants, some members have been discovered in microorganisms.