80% |
With sodium hydroxide In dichloromethane; water at 20℃; |
2.4.1. Synthesis of (4-((E)-2-(5-((E)-4-(5-(4-tert-butylphenyl)-1,3,4-oxadiazol-2-yl)styryl)thioph en-2-yl)vinyl)phenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (2TVPO)
A mixture of phosphonium salt (2) (1 g, 0.00158 mmol) andthiophene-2,5-dicarbaldehyde (0.42 g, 0.00315 mmol) were taken inWater:DCM(40:60)mixture under vigorous stirring. Sodiumhydroxidesolution (50%, 0.65ml)was added to themixture by syringe and stirredfor 5-6 h at room temperature. Completion of reaction was confirmedby TLC. The reaction mixture was diluted with dichloromethane andwater. The organic layer was separated and the solvent was removedunder reduced pressure. The resulting solidwas dried and recrystallizedfrom ethanol to get the desired product in 70-80% yield. The syntheticapproach is highly convenient and provides compound 2TVPO in thetrans configuration across the double bond. The trans configuration isevidenced by 1H NMR spectroscopy. The compound 2TVPO displayeda doublet signal around 6.5-7.5 ppm with a typical coupling of ca.16.00-16.60 Hz. This value corresponds with the expected value for a3Jtrans coupling of the vinylic protons. Further evidence concerning thestructure of 2TVPO was obtained by 13C NMR. The good accordance betweencalculated and expected values formicroanalysis gives a proof ofthe purity of the material.Yellow solid; yield: 80%; m.p. 210-215 °C; FT-IR (KBr, cm-1): 3082(C_CH), 3028 (CH aromatic), 2957, 2928 (CH aliphatic),1605, 1547, 1490, 1415 (C_C and C_N aromatic), 1016, 962 (1,3,4-oxadiazole ring), 933 (thiophene ring), 842 (tert-butylbenzene); 1HNMR (400 MHz, CDCl3) δ 8.12 (d, J = 8.4 Hz, 4H, Ar-CH), 8.08 (d, J =8.6 Hz, 4H, Ar-CH), 7.63 (d, J = 8.4 Hz, 4H, Ar-CH), 7.56 (d, J = 8.5 Hz,4H, Ar-CH), 7.33 (d, Jtrans = 16.0 Hz, 2H, trans-CH), 7.06 (s, 2H,thiophene-CH), 6.97 (d, Jtrans = 15.8 Hz, 2H, trans-CH), 1.38 (s, 18H,Ar-C(CH3)3); 13C NMR (101 MHz, CDCl3) δ 164.65, 164.26, 155.27,140.12, 129.62, 128.28, 127.62, 127.33, 127.23, 126.83, 126.10, 124.64,123.84, 121.15, 31.15, 29.72; HRMS: m/z [M + H]+ calc'd forC44H40N4O2S 688.8790, found 688.8935. |