| The Suzuki cross-coupling reaction is one of the most important methods for the construction of carbon-carbon bonds. It has been an extremely powerful tool in organic chemistry due to its mild reaction conditions, good group toleration and high yields. There are many reports on the palladium-catalyzed Suzuki cross-coupling reactions. Compared with palladium catalysts, nickel catalysts are more stable and have better activation on aryl chlorides. Therefore, they are ideal catalysts for Suzuki cross-coupling reaction. However, nickel-catalyzed Suzuki cross-coupling reaction is rarely reported, because Ni(II) is difficult to be reduced to Ni(0), and Ni(0) is more active than the Pd(0) species. Herein, the Ni-catalyzed cross-coupling reaction of aryl chlorides with arylboronic acids in isopropanol (IPA) was studied. Having screened ligands, we found that the P,0 bidentate ligand could effectively catalyze the Suzuki cross-coupling reaction. During the reactions, the dehalogenation reaction of aryl chlorides and the addition reaction of arylboronic acids to carbonyl compounds were also found. The dehalogenation of aryl chlorides represents a new method in solving of the high toxicity of polychlorinated biphenyls on environment, and biarylmethanols as important organic intermediates possess good perspective applications in organic synthesis, so the addition reaction of arylboronic acid with aldehyde and dehalogenation of aryl chlorides are worth studying. Herein, the two new synthetic methods were developed, as a result, the dehalogenation and addition products were obtained in high yield respectively by controlling the reaction condtions.1. In this dissertation, the effect of different ligands on the Ni-catalyzed Suzuki cross-coupling reaction of 4-chloroacetophenone with phenylbornic acid was examined. Ph2PCH2CH2OH was found to be the best ligand and the cross-coupling product was obtained in a yield of 99%. Complex 56 was synthesized and its approximately octahedral geometry configuration was detected by X-ray crystallographic analysis. Two Ph2PCH2CH2OH ligands chelate to nickel to form two five-membered rings, and one chlorine anion and one water molecule coordinated to the same nickel atom, another Cl- was located as a counter ion. Under the optimization reaction conditions, complex 56 catalyzed the Suzuki cross-coupling reaction of aryl chlorides that possessed electron-withdrawing group in a high yield of 90%. When aryl chlorides possessed an electron-donating group, the yield was down to approximately 60%. Moreover, complex 56 also showed good catalytic activity in the Suzuki cross-coupling reaction of multi-chlorinated arenes, the main product was the multi-coupled product.2. In the Suzuki cross-coupling conditions, the dehalogention product of 4-chloroacetophenone was found. Based on the dehalogenation reaction mechanism, the first step was the oxidative-addition reaction of Ni(0) active species with aryl chloride. Therefore, we directly employed trans-Ni(PPh3)2(l-Nap)Cl(57) as precatalyst. Complex 57 and PCy3·HBF4 catalyzed the dehalogenation reaction of diverse aryl chlorides in situ at room temperature in a yield of over 86%. We synthesized a new complex trans-Ni(PCy3)2(1-Nap)Cl(58). Its configuration is a slightly distorted square-planar geometry with two PPh3 in trans-fashion, which was detected by X-ray crystallographic analysis. The Ni-C distance of complex 58 is longer than complex 57, showing that the Ni-C bond of complex 58 is easier to break, meaning that the reductive-elimination reaction occurs easily. The experiment showed that the complex 58 was more active than complex 57.3. In the Suzuki cross-coupling conditions, we also found that if there was a carbonyl group linked to aryl chlorides, we could pinpoint the addition product of arylboronic acid to carbonyl compounds. Regarding the activity of nickel salts, the order was Ni(ClO4)2·6H2O> Ni(OAc)2·4H2O>NiCl2·6H2O, the bulky and electronegative anion improved the addition reaction. The Ni(ClO4)2·6H2O catalyzed addition reaction of arylboronic acids to aromatic aldehydes produced yields ranging from 72% to 92%. Electron-withdrawing groups either linked to aldehydes or arylboronic acids promoted the addition reaction, electron-donating groups either linked to aldehydes or arylboronic acids went against the addition reaction. Complex 60 exists in a slightly distorted tetrahedral geometry, which was detected by X-ray crystallographic analysis. Complex 60 not only catalyzed the addition reaction of arylboronic acids to aromatic aldehydes in high yields, but also catalyzed the addition reaction of arylboronic acids to aromoatic ketones, the higest yield was 67%.4. The internal relation and distinction of Suzuki cross-coupling reaction, dehalogenation reaction and addition reaction were demonstrated based on the mechanisms. The three reacions are all nickel-catalyzed reactions, the active species of the Suzuki cross-coupling reaction and the dehalogenation reaction are Ni(0) complexes, while the active species of the addition reaction is Ni(Ⅱ) complex.
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