Dicyclohexylphenylphosphine in heck coupling / Siti Salina Munandar @ Abdul Aziz

This study investigates the efficiency of dicyclohexylphenylphosphine 1 among the ligands used in the Heck coupling reaction. The method used includes the protection of iodophenol 3 by acetylation prior to the Heck reaction. 1.0 g of 4-iodoacetoxybenzene 5 (0.0038 mole) was reacted with 0.6 ml of 3, 4-dimethoxystyrene 6 (0.0038 mole) in the presence of 0.0673 g of palladium (II) dichloride (0.00038 mole), 0.2085 g of dicyclohexylphenylphosphine 1 (0.00076 mole), 0.6455 g of mercury nitrate (0.0038 mole), and 0.4848 g of potassium acetate (0.00494 mole). The reaction was left stirred under Nitrogen flow for 24 hours. The product obtained, 3, 4-dimethoxy-12- acetoxystilbene 7 (0.0038 mole) was extracted using liquid-liquid chromatography and was purified by using preparative TLC with 80 hexane: 20 ethyl acetate solvent system. Three bands were discovered: band 1 (0.0260 g), band 2 (0.0143 g) and band 3 (0.0029 g). They were then dissolved in chloroform-D and put into NMR tubes to be analyzed by using the 1H NMR spectrometer. The 1H NMR results show that the first band is best to represent 3, 4-dimethoxy-12-acetoxystilbene 7 (0.0038 mole) with the percentage yield of 2.3%. Another study that investigated the efficacy of cyclohexyldiphenylphosphine 8 as a ligand in Heck coupling produced 39.83% yield of the same product. Thus, dicyclohexylphenylphosphine 1 can still be used in Heck coupling reaction, even though it does not perform satisfactorily. However, the low yield of 3, 4-dimethoxy-12- acetoxystilbene 7 might be due to the short time spent for the reactants to optimize their coupling reaction ( 1 day), compared with the study on cyclohexyldiphenylphosphine 8 where the reaction was left for 7 days. Therefore, increasing the reaction time to about 7 days may increase the percentage yield of the 3, 4-dimethoxy-12-acetoxystilbene 7.