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A Josiphos ligand is a type of chiral diphosphine which has been modified to be substrate specific and is widely used for enantioselective synthesis.〔()H-U. Blaser, W. Brieden, B. Pugin, F. Spindler, M. Studer and A. Togni, Top. Catal ., 2002, 19, 3.〕 They are named after the technician who made the first one, Josi Puleo.〔''Privileged Chiral Ligands and Catalysts'' Qi-Lin Zhou 2011〕 ==History== Homogeneous catalysis often are used for enantioselective transformations. The ligands carry chiral information and thus they are modifyied for individual substrates. Ligands can also influence the chemoselectivity of the catalyst. The Josiphos ligands, often called privileged ligands, are important because of their ability to give high yields in enantioselective synthesis.〔()Spessard, Gary and Miessler, Gary (2010). Organometallic Chemistry: Second Edition. pp. 378-379.〕〔()Elschenbroich, Christopher (2006). Organometallics: Third Edition. pp.518-519〕 Josiphos ligands were developed in the 1990s by Antonio Togni in studies on ferrocenyl ligands previously discovered by T. Hayashi (1986). These studies focused of an Au(I)-catalyzed aldol reaction at The Central Research Laboratories of the former Ciba (now Novartis). Diphosphine ligands were prepared with secondary phosphines, they are today known as Josiphos ligands family, which gets the name after Josi Puleo, the technician who prepared the first one. It was first tried in an Ru-catalyzed enamide hydrogenation synthesis resulting in ee’s higher than 99% and TOF of 1000h−1.〔Cai, C., Rivera, N.R., Balsells, J., Sidler, R.S., MC Williams, J.C., Schultz, C.S and Sun Y, Org. Lett, 2006, 8, 5161〕 Coupling with Grignards and Negishi coupling reactions〔()Limmert, M.E., Roy., A.J and Hartwig J.F, J. Org. Chem, 2005, 70, 9364〕〔()Alvaro, E and Hartwig, J.F, J. Am. Chem. Soc, 2009, 131, 7858〕 A variety of Josiphos ligands are commercially available, under licence from Solvias. The (R-S) and its enantiomer are commonly used because they have provide give higher yields and higher enantioselectivities than the diastereomer (R,R).〔Zhou Q.L, (2011). Privileged Chiral Ligands and Catalyst. pp.93-127〕〔Thommen, M and Blasr, H.U Pharma Chem, 2002, 33-34〕 The ferrocene scaffold has proved to be versatile.〔Blaser, H.U., Malan,C., Pugin, B., Spindler, F.,Steiner, H., and Studer, M, 2003. Adv. Synth. Catal, 345, 103-152〕〔Zhou Q.L, (2011). Privileged Chiral Ligands and Catalyst. pp.93-127〕〔()Whitesell, J.K Chem. Rev,. 1989, 89, 1581〕〔Inoguchi, K., Sakuraba, S., and Achiwa, K. Synlett, 1992, 169〕〔()Chen, W. and Blaser, H.U 2008 in Trivalent Phosphourus compunds in Asymmetric Catalyst: Synthesis and applications. (e.d. A. Borner) pp. 359-393〕〔() Zhou Q.L, (2011). Privileged Chiral Ligands and Catalyst. pp.93-127〕 One structural parameter that influences reactivity is the bite angle. The P1-M-P2 angle has an average value of 92.7°.〔 View of general conformation of a Josiphos ligands complex Figure 3: View of general conformation of a Josiphos ligands complex The general consensus for the naming is abbreviating the individual ligand as (R)-(S)-R2PF-PR’2. The substituent on the Cp is written in front of the F and the R on the chiral center after the F.〔()H-U. Blaser, W. Brieden, B. Pugin, F. Spindler, M. Studer and A. Togni, Top. Catal ., 2002, 19, 3.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Josiphos ligands」の詳細全文を読む スポンサード リンク
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