Practical Synthesis of New Chiral Monophosphine Ligand MOP for Catalytic Asymmetric Reactions

含光学活性膦配体的过渡金属络合物催化的不对称反应因其合成用途而引起人们极大的兴趣。手性配体的开发是催化不对称合成研究中最令人兴奋和最具挑战性的课题之一，它将在催化活性和对映体选择性方面与给定的反应有效地匹配。我们开发了以2-(二苯基膦)-2‘-甲氧基-1，1’-联萘(MeO-MOP)为代表的新型单齿膦配体，其手性源于联萘的轴向手性。轴手性单膦配体MOPS被发现对钯催化的三种新型不对称反应非常有效：1)烯烃的不对称硅氢化反应，这为合成光学活性醇提供了一条新的有效途径。2)1，3-烯炔的不对称硼氢化反应，得到光学活性的烯基硼烷。3)甲酸对烯丙基酯的不对称还原。从光学活性2，2‘-双(羟基)-1，1’-联萘入手，阐述了大规模合成MOP配体的方法。通过钯或镍催化的交叉偶联反应，制备了在2‘-位含有多个取代基的新的MOP衍生物。

Asymmetric reactions catalyzed by transition metal complexes containing optically active phosphine ligands have attracted significant interest for their synthetic utility. One of the most exciting and challenging subjects in research on the catalytic asymmetric synthesis is development of the chiral ligand which will fit in with a given reaction efficiently in catalytic activity as well as in enantioselectivity. We have developed new monodentate phosphine ligands represented by 2- (diphenylphosphino) -2'-methoxy-1,1'-binaphthyl (MeO-MOP), whose chirality is due to the binaphthyl axial chirality. The axially chiral monophosphine ligands MOPs were found to be very efficient for three types of new palladium-catalyzed asymmetric reactions : 1) Asymmetric hydrosilylation of olefins which provides a new efficient route to optically active alcohols. 2) Asymmetric hydroboration of 1,3-enynes giving optically active allenylboranes. 3) Asymmetric reduction of allylic esters with formic acid. We have elucidated the preparation methods for MOP ligands in a large scale starting with optically active 2,2'bis (hydroxy) -1,1'-binaphthyl. Preparation of new MOP derivatives bearing several substituents at 2'-position were also achieved by use of palladium-or nickel-catalyzed cross-coupling type reactions.