Synthesis and Characterization of New Coumarin Substituted Chromone (8-Methyl-4-phenyl-2H,10H-pyrano[2,3-f] chromene-2,10-dione) Using Benzyl Acetoacetate and Studied their Fluorescence Properties

Copyright: © 2018 Chaudhari PS, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Synthesis and Characterization of New Coumarin Substituted Chromone (8-Methyl-4-phenyl-2H,10H-pyrano[2,3-f] chromene-2,10-dione) Using Benzyl Acetoacetate and Studied their Fluorescence Properties

Fluorescent compounds play an important role in solid state lighting, solar energy conversion and as biomarkers in the life sciences [5][6][7][8][9][10]. Fluorescent heterocyclic compounds are of immense interest as functional materials in the emitters of electroluminescence devices and in the molecular probes used for biochemical research, as well as in the traditional textile and polymer fields [11][12][13]. Heterocyclic fluorophores are useful materials in the search for new biologically active compounds and diagnostic methods [14]. Coumarin fluorescent probes or labels have extensive and diverse applications, as they exhibit extended spectral range and high emission quantum yields [15]. Coumarin-based fluorescent chemo dosimeter with salicylaldehyde functionality was used as a binding site for selective detection of cyanide anions over other anions in water at biological pH. Coumarin core moieties have wide biological application in particular for the imaging of living cells [16]. The coumarins have been promising candidates for the applications in molecular electronics and biological imaging [17].
In present research, we have developed new ecofriendly synthetic pathway for the synthesis of coumarin substituted chromone and further studied of their fluorescence properties which can influence their optical application. instrument using the ATR technique and the spectrum was obtained in the wavelength range of 4000-600 cm -1 . BRUKER AVANCE II 400 the spectra were calibrated according to the solvent signals: 7.26 ppm for CDCl 3 , 2.50 ppm for DMSO-d 6

Synthesis of 7-Hydroxy-4-phenyl-2H-chromen-2-one (Pechmann condensation):
A 100 ml Erlenmeyer conical flask equipped over magnetic stirrer was charge with resorcinol (2 gm) containing Benzyl acetoacetate 2.36 (gm) is added concentrated H 2 SO 4 (4 ml) below 10°C with constant stirring. Afterward, the reaction was continuing over the period of 0 to 5 hours in anhydrous condition. The progress of the reaction was monitored by TLC. On completion of the reaction, the reaction mass was poured over crushed ice resulted in the formation of yellow amorphous solid. The formed solid was filtered, washed with water, dried and crystallized from ethanol. The yield of product was found to be 94%. Melting point 215°C (Scheme 1).

Synthesis of 2-oxo-4-phenyl-2H-chromen-7-yl acetate (Acetylation):
In a 100 ml round bottom flask equipped with magnetic stirrer was charge 7-hydroxy-4-methyl-2-H-chromen-2-one (1gm), NaOH (1 gm) and acetyl chloride (1.5 gm). The reaction mass stirred gently over the time of 3 hours at room temperature, the progress of the reaction was monitored by TLC. On completion of the reaction, the reaction mass was poured over crushed ice resulted in the formation of brown amorphous solid. The formed solid was filtered, washed with water, dried and crystallized from ethanol. The yield of product was found to be 88%.

Synthesis of 8-acetyl-7-hydroxy-4-phenyl-2H-chromen-2-one (Fries rearrangement):
100 ml round bottom flask equipped with a reflux condenser with 4-methyl-2-oxo-2H-chromon-7-yl acetate (1 gm), in a catalyst AlCl 3 (1 gm), reflux for 2 hours in an oil bath and maintained the temperature 135 to 145°C then add 1% HCl for 12 hours. The progress of the reaction was monitored by TLC at room temperature. On completion of the reaction, the reaction mass was poured over crushed ice resulted in the formation of black crystalline solid. The formed solid dried and crystallized from ethanol. The yield of product was found to be 86%.

Results and Discussion
In this work, we report the synthesis of coumarin substituted chromone and investigated their influence on fluorescence properties.
All the products were characterized by IR, 1H NMR and MS analysis. FTIR spectral characterization of compound (6) show absorption bond correspond the 1739 cm -1 for v(C=O) stretching of coumarin moiety. The most prominent bond due to (-C-O-C) aromatic stretch occurs at range 1134(s), 1215(s) cm -1 . It is generally occurring at 1000-1300 cm -1 . The characteristics absorption peak at 1604 cm -1 assign to v (C=C) aromatic stretch. and 3074 (m) aromatic -CH strect. 1 H NMR spectra of compound (6) in CDCl 3 showed chemical shifts for CH 3 (6) reveals that synthesized compound a wider transparency range extending into entire visible and absorbance takes place in the UV range 223 nm to 301 nm and the cut off wavelength (X cm-off) within the range between 329 to 223 nm in benzyl acetoacetate with λ-max was found to be 301 nm. This absorbance maximum is to be assigned to π→π*, n→π* transition and may be attributed to the excitation in the aromatic ring and C=O group.
From all above observation, spectral properties and analytical data was confirmed the structure as coumarin substitute chromone. The result obtained in the present study shows that this information would give rise to design of better molecule with good yields, developed of new synthetic green strategies and efficient is desirable for the synthesis of coumarin substituted chromone.

Fluorescence properties of coumarin substituted chromone
In this work, we present simple new fluorescents coumarin substituted chromone synthesis and we utilized the unique advantages of simple coumarin substituted chromone as a fluorescent compound, the approach of the synthesis these fluorescent compounds are demonstrated in Scheme 1. The studies of fluorescence were performed in ethanol at a concentration of 1.0 × 10 -5 and studied Excitation spectra, emission spectra and stoke shifts (nm) of all compounds (Figures 1-8), were determined via comparison method [18,19]. Fluorescence spectra were obtained at their respective maximum excitation wavelength in Coumarin substituted chromone an electron-donating group was known to exhibit strong fluorescence.

Conclusion
In this paper we have successfully synthesized the coumarin substitute chromone and well characterized by the 1 H NMR, FT-IR and Mass spectroscopic analysis and the result obtained in the present study shows that this information would give rise to design of better molecule with good yields, developed of new synthetic green strategies. Further we have checked its fluorescence properties. It has been conclude that compounds 3 to 6 show fluorescent in ethanol with high emission, excitation and show high activity. This work is useful for the synthesis of same type of compound and also useful in the fluorescence studies.