[CH:1](=[O:10])[CH:2]=[CH:3][C:4]1[CH:9]=[CH:8][CH:7]=[CH:6][CH:5]=1.C(C1C(=O)C(Cl)=C(Cl)[C:15](=[O:16])[C:14]=1C#N)#N.CCO.O.[O-2].[O-2].[O-2].O=[Si]=O.O=[Si]=O.O=[Si]=O.O=[Si]=O.[Al+3].[Al+3]>C1(C)C=CC=CC=1>[C:1]([O:16][CH2:15][CH3:14])(=[O:10])[CH:2]=[CH:3][C:4]1[CH:9]=[CH:8][CH:7]=[CH:6][CH:5]=1A homogeneous mixture containing cinnamaldehyde (7.5 mmol), DDQ (11.3 mmol), EtOH (15 mL) and toluene (10 mL) is taken in a round bottom flask and catalytic amount of AMBERLYST® 15 (0.1 g) is added to it. The mixture is refluxed for 6 hrs under Dean Stark apparatus. After completion of the reaction (observed by TLC and by GC analysis), the reaction mixture is filtered and washed with EtOH (10 ml×2). Concentrate the filtrate under reduced pressure and the crude product thus obtained is loaded on a neutral alumina column and eluted with diethyl ether. Ethyl cinnamate (from formula I where X1═H, X2═H, X3═H, X4═H, X5═H, R═C2H5) is isolated in 94% yield. 1H-NMR (CDCl3, 300 MHz) δ7.72 (1H, d, J=16.19 Hz), 7.43 (5H, m), 6.47 (1H, d, J=16.19 Hz), 4.28 (2H, q, J=7.09 Hz), 1.34 (3H, t, J=7.09 Hz); 13C-NMR (CDCl3, 75.4 MHz) δ166.9, 144.5, 130.1, 128.8, 128.5, 127.9, 118.2, 60.4, 14.2.
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