Microwave-induced , Iodine-alumina catalyzed transformations of 1-( 2 '-hydroxyaryl )-3-( 2-chloroquinolin-3-yl )-prop-2-en-1-one

The chalcone derivatives, 1-(2'-hydroxyaryl)-3-(2-chloroquinolin-3yl)-prop-2-en-1-one was transformed to corresponding flavone derivatives by iodine impregnated neutral alumina under microwave irradiation. The synthesized flavone derivatives were structurally confirmed by elemental analysis, UV, IR and H-NMR spectral data, and the notable yield obtained was compared with previously reported method.

It has been observed that the substitution of five or six member heterocyclic group in C-2 position instead of phenyl group improves the biological activity of flavones [7][8][9] .Similarly, microwave (MW) irradiation is an efficient and environmentally-benign method to activate various organic transformations to afford products in higher yields in shorter reaction periods.Owing to its immense importance, we planned to synthesize new substituted flavone derivative, which was catalyzed by iodine impregnated neutral alumina (Al 2 O 3 ) under microwave irradiation.

Experimental
All the common chemicals were obtained from Merck chemical company, SD fine chemicals and Sigma-Aldrich chemicals, India.The chalcone (3a-e) were prepared according to the procedure stated already. 10 Samsung domestic microwave oven was used at 400W power level for all the experiments.TLC was carried out using and spotting was done using iodine or UV light.Melting points of synthesized compounds were determined in open glass capillaries and were uncorrected.
UV spectra were recorded using Perkin-Elmer 402 UV-vis spectrophotometer.IR spectra were recorded on Perkin-Elmer 577 IR spectrophotometer using KBr pellets. 1 H spectra were recorded on Brucker 300 MHz NMR Spectrometer in CDCl 3 with tetramethyl silane as the internal standard and the chemical shifts were reported in ppm scale.Mass spectra were studied using Finnigan MAT 8230 mass spectrometer.Elemental analysis were done on Vario EL-III elemental analyzer and the analyzed reports were within ± 0.4 % of the theoretical values.

Synthesis of heterogeneous catalyst I 2 -Al 2 O 3
2.538 g (10 mmol) iodine was dissolved in minimum quantity of solvent dichloro methane.Then, 25 gm of neutral was added to iodine solution to adsorb.The mixture was air dried and stored in glass bottle until use.

Results and Discussion
Our earlier work 10  The UV-vis absorption spectrum of the compounds 4a-e in CHCl 3 showed  max at 265-275 nm and 358-386 nm indicating the presence of flavone moiety.IR spectra of compounds 4a-e showed the absorption at 1664-1668 cm -1 for carbonyl groups and absence of hydroxyl absorption confirmed the oxidation of hydroxyl groups in chalcones 3a-e.It was further supported by not observing corresponding 1 H NMR signals.The C-3 proton gave singlet about  6.42-6.44 ppm for the compounds 4a-e showed that the C  -H of corresponding chalcone involved in cyclization of chalcone to form corresponding flavone.The entire mass spectral data and elemental analysis data were in accordance with the structure of expected compounds 4a-e and they were given in experimental part.
On comparison of physical data, synthesis of compounds 4a-e catalyzed by I 2 /Alumina under microwave condition gives comparably high yield with short time among the other conventional methods 11 , and the physical data were given as given in Table 1.