Bis (Imidazolinyl) Phenyl-Pincer Platinum And Palladium Complexes And Their Application In Asymmetric Friedel-Crafts Alkylation Reaction

In this thesis, four chiral bis(imidazoline) ligands 3a-,d have been synthesized in three steps starting from 1,3-benzene dicarbonyl dichloride and amino acids. And one pincer palladium(II) complex 4, four pincer platinum (II) complexes 5a-d, three pincer platinum (II) complexes 6a-c, and one cationic pincer platinum (II) complex 7 were synthesized based on the ligands 3a-d with Pd(OAc)2 or K2PtCl4. All the new compounds were fully characterized. The catalytic activities of the cationic pincer platinum (Ⅱ) complex in the asymmetric Friedel-Crafts alkylation of indoles with nitroalkenes were studied. The main results are as follows:1. In the first instance, the chiral amino alcohols were obtained from the correspounding chiral amino acids through reduction system of NaBH4/I2. Then the 1,3-benzene dicarbonyl dichloride reacted with amino alcohols in the presence of Et3N in THF at room temperature to afford the corresponding amido alcohols 2a-c. 2,6-bis(imidazoline)benzene ligands 3a-d were obtained from the amino alcohols 2a-c and aliphatic amines as shown in Scheme 1. All the new compounds 3a-d were characterized by IR, MS,1H NMR,13C NMR, HSQC and HRMS spectra.2. The pincer palladium(II) complex 4 and platinum(II) complexes (Pt-Cl) 5a-d were successfully synthesized by direct cyclometalation reaction of 2,6-bis(imidazoline)benzene ligands 3a-d with Pd(OAc)2 or K2PtCl4 in dried acetic acid, and the pincer platinum (II) complexes (Pt-I) 6a-c were obtained by reaction of pincer platinum(II) complexes (Pt-Cl) 5a-c with excess KI. Halide abstraction on 6a proceeded in CH2Cl2/H2O with AgOTf to give platinum cationic complexe 7 (Scheme 2). All of the nine chiral N-alkyl-1,3-bis(2-imidazolinyl)benzene-derived pincer complexes were new compounds and characterized by elemental analysis, IR, MS,1H NMR and 13C NMR. The molecular structures of the compounds 5c and 6c were further confirmed by single-crystal X-ray analysis.3. We investigated the application of pincer cationic platinum(II) complex 7 as catalyst for asymmetric Friedel-Crafts alkylation reactions between indoles and trans-β-nitrostyrenes (Scheme 3). The optimized reaction condition was 5 mol% 7 as the catalyst in toluene at 0℃for 36 h under N2 atmosphere, giving the product in a good yield (80%) and moderate enantioselectivity (78% ee). The scope of the alkylations of indoles with nitroalkenes was explored at the optimized conditions, and various types of the nitroalkylatedindoles were obtained in moderate yields (50-80%) and moderate enantioselectivities (up to 83% ee).