Synthesis And Application Of Dimethylmalonic Acid-derived Chiral Bidentate Nitrogen Ligands

In this thesis, we have synthesized ten dimethylmalonic acid-derived chiral bidentate nitrogen ligands and four cationic pincer platinum complexes using chiral amino alcohols as the chiral sources. The new compounds were characterized by spectroscopic methods. The potential of the new ligands in the asymmetric Friedel-Crafts alkylation of nitroalkenes with indoles and Michael addition of1,3-dicarbonyl compounds to nitroalkenes were investigated. The main results are as follows:1. Synthesis and characterization of dimethylmalonic acid-derived chiral bidentate nitrogen ligandsTreatment of dimethylmalonic acid with SOC12gave dimethyl malonyldichloride, which reacted with2equiv. of optically active amino alcohol to afford the corresponding chiral amido alcohols. Then SOC12was added to amido alcohols and refluxed. After removal of excess SOC12under reduced pressure, amines were added and stirred for24h, followed by addition of15%aqueous NaOH. The obtained mixture of1and2was refluxed in THF-CH3OH in the presence of NaOH to produce chiral bidentate nitrogen ligands la-j (Scheme1). la-j were new compounds, which were characterized by MS, HRMS, IR,1H NMR,13C NMR, HSQC spectra.2. Applications of chiral bidentate nitrogen ligands in the asymmetric Friedel-Crafts alkylationTrans-β-nitrostyrene was chosen to react with indole for optimizing reaction conditions. The optimal reaction conditions are as follows:trans-β-nitrostyrene reacted with indole (1:5) in the presence of10mol%Cu(OTf)2/12mol%1a in toluene at room temperature for48h under N2atmosphere, giving the product in an excellent yield (99%) and good enantioselectivity (85%ee). The reactions of a variety of nitroalkenes and indoles were investigated under the optimal conditions (Scheme2). It was found that the nitroalkylated indoles were obtained with excellent yields (up to98%) and high enantioselectivities (up to88%ee, up to96%ee after recrystallization).3. Applications of chiral bidentate nitrogen ligands in the asymmetric Michael additionDimethyl malonate was chosen to react with trans-β-nitrostyrene for optimizing reaction conditions. The optimal reaction conditions are as follows:dimethyl malonate reacted with trans-β-nitrostyrene (2:1) in the presence of10mol%NiBr2/12mol%1a in toluene for48h under N2atmosphere, affording the product in a good yield (86%) and good enantioselectivity (80%ee). The reactions of a variety of nitroalkenes and1,3-dicarbonyl compounds were investigated under the optimized conditions (Scheme3) and the addition products were obtained with up to94%yield and81%ee.4. Synthesis and characterization of cationic pincer platinum complexesWe synthesized chiral imidazoline ligands according to the method reported by us, which reacted with K2PtCl4by direct cyclometalation to produce the neutral NCN pincer chloroplatinum complexes. The cationic platinum aquo complexes4a-b were prepared by the reaction of Pt-Cl complexes with H2O in the presence of TlOTf. The cationic platinum pyridine complexes5b-c were prepared by the reaction of Pt-Cl complexes with pyridine in the presence of AgOTf (Scheme4).3a,4a-b,5b-c were new compounds, which were characterized by MS, HRMS, IR,1H NMR,13C NMR and elemental analysis. The cationic pincer platinum complexes were applied to the asymmetric Friedel-Crafts alkylation of indole with trans-β-nitrostyrene, affording the product with up to80%yield and60%ee.