An Axially Chiral Biphenyl Diamine: The Synthesis With Central-to-axial Chirality Transfer And Applications In Catalytic Asymmetric Reactions

Asymmetric catalysis is one of the most efficient and convenient methods for preparing a wide range of enantiomerically pure compounds. It is a powerful component of modern synthetic organic chemistry. Chiral catalyst is the source of product Chirality. It is one of the main tasks of asymmetric catalysis to develop new effective chiral catalysts. Economic preparation and high effect stucture are crucial for chiral catalyst. In this text, an new biphenyl diamine has been synthesized, and was used in asymmetric reactions. The content of full text is as follows:1. A C2-symmetric atropisomeric chiral diamine (R,R,Sax)- PD-BIPHAM ((Sax)-[6,6’-(2R,4R-pentadioxy)]-1,1’-biphenyl-2,2’-diamine) induced by central chirality was synthesized without resolution step. According to HPLC analysis,97% ee was determined for the derived (R,R,Sax)-PD-BIPHAM and therefore 98.5:1.5 diastereo- selectivity was generated in the stereoselective Ullmann coupling reaction. It showed that the diastereoselective was highly controlled for this intramolecular Ullmann coupling. By single-crystal x-ray diffraction of crystal of derived (R,R,Sax)- PD-BIPHAM, the molecular configuration was confirmed.2. We extended the application of (R,R,Sax)-PD-BIPHAM to the synthesis of bis(aminophosphine) ligand. The ligand was found to be highly effective in the asymmetric hydrogenation of N-alkyl-a-enamino-esters. in 100% yield and up to 97% ee. The chiral bridge restricted the change of the ligand conformational and made it more rigid than other bis(aminophosphine) ligand without chiral bridge. And also the chiral bridge controled ligand dihedral angle, which in turn caused a great influence on ligand bite angle. It was highly advantageous to stereoselectivity in the synthesis of asymmetric hydrogenation.3. We have developed a N,N’-dimethyl (R,R,Sax)-PD-BIPHAM organocatalyst for exo-selective Diels-Alder reaction ofα,β-unsaturated aldehydes with cyclopentadiene, and excellent levels of exo-selectivity were obtained.. It was observed that the introduction of phenyl groups at the 3- and 3’- positions of the biphenyl moiety showed particularly good levels of exo-selectivity and enantioselectivity. With this catalyst, excellent levels of exo-selectivity were obtained. Diastereoselectivity observed was up to 9.3:1 and enantioselectivity was up to 97% in favor of the exo-cycloadduct. Plausible mechanism and possible transition-state models for the exo-selective asymmetric Diels-Alder reaction were discussed.