Malleshwar Darbarwar

Absorption and fluorescence spectra of 7-aminocoumarin derivatives

Abstract The absorption and fluorescence spectra of twelve 7-aminocoumarin derivatives have been studied with methanol and chloroform as solvents. Electronic transitions to nπ * states have been traced. The effect of different substituents on the nitrogen was easily observed in the fluorescence spectra. Fluorescence quantum yields and oscillator strengths were evaluated. The role of hydrogen bonding on emission maxima, quantum yields and photolytic dissociation were discussed.

A Convenient Synthesis of 3-Aryl-4-oxo-4,5-dihydro Furo [3,2-c] Quinolines

Abstract Furo [3,2-c] quinolines (4a-f) were prepared by a convenient new method involving cyclodehydration of s-ketoethers (3a-f) of quinolones, which were obtained by the reaction of 4-hydroxy quinolin-2(1H)-ones (1) with phenacyl bromides (2).

Synthesis of 6H-[1]-Benzopyrano[3,4-h]-1,6-Naphthyridine-5,7-Diones

Abstract Hitherto unreported 6H-[1]-benzopyrano[3,4-h]-1,6-naphthyridine-5,7-diones have been accomplished (4a-f) by an intramolecular cyclodehydrochlorination reaction of 3-(2′-chloro nicotinamido)-2H-1-benzopyran-2-ones (3a-f) obtained by the reaction of 3-amino coumarins (1a-f) with 2-chloronicotinoyl-chloride (2).

Synthesis of [1]Benzopyrano[3,4-c][2]benzazepine-6, 8, 13(7H)-triones

Abstract Hitherto unknown [1] benzopyrano [3,4-c] [2] benzazepine-6,8,13(7H)-triones (4a-e) have been synthesized by the intramolecular cyclodehydration of N-(2-oxo-2H-1-benzopyran-3-yl) phthalamic acids (3a-e) obtained by the reaction of 3-amino coumarins (1a-e) with phthalic anhydride (2)

One Pot Synthesis of 7-[1, 2-Dihydro-4-Hydroxy-1-Methyl/Phenyl-2-OXO-3-Quinolinyl]-5, 7-Dihydro-5-Methyl/Phenyl-6H-[1]-Benzo Pyrano [3, 2-c] Quinolin-6-Ones

Abstract The reaction of two moles of 4-hydroxy quinotin-2-ones (1) with one mole of salicylaldehydes (2) furnished 6H-benzo-pyrano-[3, 2-c] quinolin-6-ones (3a-j).

An Efficient Synthesis of 2,5-Dioxo-5,6-Dihydropyrano[3,2-c]-Quinolines

Abstract A regiospecific route for 2,5-dioxo-5,6-dihydropyrano [3,2-c]-quinolines 4a-p has been developed by base catalysed reaction of 4-hydroxy-3-formyl quinolin-2(1H)-one 2a-c with active methylene compounds 3a-f in good yield.

Synthesis of 7H-8, 9-Dihydro-4,8-Dimethyl-Pyrano[2,3-e]Indol-2-Ones

Abstract The synthesis of pyrrolocoumarins viz., 7H-8,9-dihydro-4,8-dimethyl-pyrano[2,3-e]indol-2-ones, a new tricyclic system (5), have been achieved from 7-amino-4-methylcoumarin (1) by tosylation, allylation and neat pyrolysis. A plausible mechanism involving amino-Claisen rearrangement followed by [3:3] sigmatropic shift has been presented.

Synthesis of 3-(2H-Indazol-2-yl)-2H[1]-Benzopyran-2-Ones

Abstract Hitherto unknown 3-(2H-Indazol-2-yl)-2H[1] benzopyran-2-ones (4a-f) have been synthesized under the trithyl phosphite (TEP) mediated reaction conditions of 3-[[(2-nitro-phenyl)-methylene]amino]-2H-1-benzopyran-2-ones (3a-f), obtained by the condensation of 3-amino coumarins (1a-f) with 2-nitro-benzaldehyde (2).

A new route to the synthesis of coumestans

2-Chlorocyclohexanone ~ was refluxed with 4-hydroxy coumarin in molar proportions in boiling xylene using anhydrous potassium carbonate a s a basic condensing agent for four hou.rs. At the end of the reaction, the xylene solution was decanted and concentrated to a small bulk when a white solid separated. The crude product was filtered and repeatedly digestea with aqueous sodium bicarbonate solution. The bicarbonate insolubles were then washed with dilate hydrochloric acid and finally with water, free from lhe acid.. The crude product thus obtained was recryst2Alised from methanol, when a colourless crystalline substance with a m.p. 173 ~ C, different from starting material, was obtained. Elemental analysis indicated the absence of halogen and the compound aceounted for C15 skeleton. The I.R.. speetrum of the compound dial not reve,,l the presence of hydroxyl and showed ah absolption around 1710 cm -1 assignable to lactone carbonyl. This indicated that the hydroxyl i n 4-hydroxy-coumarin and halogen of 2-chlorocyclohexanone were involved in the condensation, in which case the resulting product must have been an ether with the carbonyl of the cyclohexyl moiety free. The compoand however did not reveal the presence of ah additional carbonyl either in I.R. of by the qualitative tests. Further, in the N.M.R. of the compound, there was no indication for the presente of a ffee proton in 3-position of .coumarin and therefore suggested that 3 and 4-positions of coumarin are involved in the condensation wittt 2-chlorocyclohexanone forming a fused 5-membered ring. From an analogy of the condensation of 2-chlorocyclohexanone with fl-naphthol reported by Osdene attd R~seP, it appeaxed probable to suppose that the reaction proceeded through ah intermediate 3-(2-oxo-cyclohexyl)-4-hy 91 coumarin (I)