Synthesis Of Chiral Bis (oxazolinyl) Ferrocene Ligands And Their Senses Of Asymmetric Induction

Chiral bis(oxazolines) and chiral ferrocenylphosphines have been respectively widely and successfully used as ligands in a variety of Lewis acid catalyzed asymmetric processes. Therefore, ferrocene derived chiral bis(oxazolines) were anticipated to show better sense of asymmetric induction. However, there are no reports so far on the utilities of bis(oxazolinyl)ferrocenes as ligands in the asymmetric reactions. In this dissertation, four of chiral l,l'-bis(oxazolinyl)ferrocenes Lip, Lph, Lbn and Lme were prepared and firstly used as N,N'-bidentate ligands in Lewis acid catalyzed asymmetric cyclopropanation and Diels-Alder reaction.The ligands were synthesized with 1,1'-ferrocenyldicarboxylic acid chloride and a series of (5)-β-amino alcohols, which were prepared by reduction of the corresponding natural L-α-amino acids using sodium borohydride-iodine as reductant system, in the presence of triethylamine and methansulfonyl chloride by a general methodology. 1,1'-Ferrocenyldicarboxylic acid chloride was prepared from ferrocene as starting material, via acylation and haloform reaction. The acylation and diacylation of ferrocene were studied intensively on the routes and conditions.The asymmetric inductions of the ligands in Cu(I) catalyzed cyclopropanation of styrene with ethyl diazoacetate (EDA) were investigated. In addition, a new system method of analyzing the diastereoselectivity and enantioselectivity of the reaction have been founded based on GLC using commercial SE-30 column and a β-cyclodextrin derived chiral column made in our lab. The ligands all showed some extent of asymmetric induction but, with a low degree. The best results of enantioselectivity was obtained with 24% ee for the trans-product. The reason of the low enantioselectivity was theoretically discussed.The ligands have also been applied to magnesium(II) or copper(II) catalyzed Diels-Alder reaction with N-acryloyl oxazolidinone and cyclopentadiene. The Lip/ Mg(ClO4)2 system has been demonstrated to be efficient which led to the cycloadduct with high endo:exo selectively (92:8) in 41% ee (2R) for the endo isomer. However, The other three ligands have the low degree of enantioselectivity (lower than 10% ee). The mechanism of asymmetric induction was analyzed.