Application of Rh Catalysts

Ligand effect on reactivity dppb dppp TFP dppe PPhg, AsPhg 

Shortly after this publication, Hayashi and coworkers [11] reported the first enantioselective variant of this transformation, achieving excellent yields and enantioselectivities. The use of the chiral phosphane ligand (S)-B1NAP (2,2 -bis(diphenylphosphino)-l,l -binaphthyl) along with RhfacacjfCjH lj makes the perfect catalyst - which is formed in situ to achieve 99% yield and 

1) Our analysis seems to indicate that of the eight prizes awarded directly or indirectly involving transition-metal-based catalysts (2010 Suzuki, Heck, and Negishi 2005 Grubbs, Schrock, and Chauvin 2001 Sharpless, Noyori, and Knowles 1983 Taube 1973 Fischer and Wilkinson 1963 Natta and Ziegler 1913 Werner and 1912 Grignard and Sabatier), three have been awarded in the last 15 years, the reader of course is welcome to dis ree with this list. 

2) Owii to the exponential rise in organocatalysis over the last 15 years, we suspect that a prize to be awarded in the near future. 

These innovative and groundbreaking findings paved the way for an intense and hot research activity on asymmetric addition reactions using transition-metal catalysts and related processes. 

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The application of Rh catalysts, which moved in the 1970s but in focus till today, allows operating the process under much milder conditions (20-120 bars, 70-160°C). Usually, the catalyst is produced from Rh(II)carboxylates, Rh(acac)(CO)2 (acac = acetylacetonate), or Rh(acac)(COD) (COD = 1,5-cyclo-octadiene). Commercial phosphorus ligands, such as monodentate phosphines (PPhg) or phosphites [P(OPh)3, P(0-o-tBuPh)3, Alkanox 240], significantly improve the activity. Simultaneously, isomerization of the starting olefin may occur. Commonly the ligand is used in an excess in comparison to the metal. 

The cycloaddition reaction is one important application of Rh catalysts. Recently, Rh-catalyzed intermolecular [5 + 2] cycloaddition/Nazarov cyclization cascade was reported by Wender et al. (Scheme 5.49) [47]. The reaction could be conducted with a single catalyst, such as [(Cj(,Hg)Rh(cod) "SbFg ] (2mol%), and provide an efficient strategy for the facile synthesis of bicyclo[5.3.0]decanes 72. 

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