Synthesis And Applications In Asymmetric Hydrogenation Of Chiral Biphenyl Diphosphines And Their Ru(Ⅱ) Complexes

The designing and synthesis of chiral phosphine ligands are continuous central focus in the asymmetric catalysis and synthesis. And the outstanding chiral phosphines are the key to attaining high enantioselectivity and to increasing catalytic activity in the asymmetric hydrogenation catalyzed by organometallic complex. This thesis focused mainly on the designing and synthesis of a series of chiral diphosphine ligands with biphenyl backbone and their application in the asymmetric hydrogenation of acetophenone catalyzed by Ru(II) complexes.Firstly, the chiral diphosphines,(i?)- and (S)-(6,6'- Dimethoxybiphenyl-2,2'-diyl)-bis(diarylphosphine) were designed and synthesized by three synthetic routes and determined by ³¹PNMR, ¹HNMR and MS.1. (R)- and (S)-(6,6'-Dimethoxybiphenyl-2,2'-diyl)bis(diphenylphosphine) (R)-and (S)-33d was synthesized by the approach A. In this approach, (RS)-(6,6'-Dimethoxybiphenyl-2,2'-diyl)bis(diphenylphosphine oxide) rac-75a are synthesized via an ortho-lithiation/iodination Ullmann reaction sequence. Instead of n-butyl lithium, the more available Grignard agents were used, so that the operation was more convenient. And the crude products were easily purified just by washing with commercially available organic reagents.2. the racemic biphenyl diphosphine ligands rac-33d, rac-33e, rac-33f and rac-33g were synthesized from commercially available 3-bromoanisole and triethyl phosphite by the approach B. Racemic rac-75a and rac-75b were resolved with (-)-or (+)- DBTA and reduced to diphosphines(R)- or (S)-33d and (R)- or (S)-33e. Inaddition, the synthesis of diethyl (3-methoxyphenyl)phosphonate 76 was improved on experimental technique. This approach is an efficient synthetic method for the biphenyl diphosphines with the different diarylphosphine group.3. A superior synthetic route C was designed for the synthesis of a series of chiral diphosphine analogues to avoid the chiral seperation for the separate prochiral diphosphine. (&S)-(6,6'-Dimethoxybiphenyl-2,2'-diyl)bis(phosphonic acid diethyl ester) rac-38 was resolved with (-)- or (+)- DBTA by fractional crystallization to obtain optical pure (R)- and (S)-3S.Secondly, a series of RuCk (diphosphine)(diamine) complexes were synthesized and characterized by 31P NMR and *H NMR.Finally, The catalytic activity and enantioselectivity of RuCl2(i?-33d)((i?,i?)D-PEN)(82) was studied for the asymmetric hydrogenation of acetophenone in the presence of KOH and 2-Propanol. The results indicated that nearly quantitative conversion and good enantioselectivity (82.6%ee) were achieved under mild conditions.