Organic Letters
Letter
(7) Ligand L1 was selected for the initial studies due to its high
catalytic performance in Rh-mediated asymmetric hydrogenations; see
ref 6b,e.
(8) Determination of the enantiomeric excess of products 2 by chiral
GC or HPLC analysis proved to be difficult. For this reason, products
2 were transformed into their benzoate esters 4 to facilitate the
(9) The P−OP ligands presented in Figure 1 can be categorized in
two principal groups: (i) geminal ligands L2−L8 (phosphine and
phosphite groups bound to the same carbon) incorporating a
stereogenic axis and further stereogenic carbon or phosphorus centers
(the Rh complexes derived from these ligands present strained
asymmetric environments around the metal center; P−Rh−PO angle
of ca. 80°; see ref 6g,i); (ii) vicinal ligands L1 and L9−L14 (phosphine
and phosphite groups bound to vicinal carbons) containing two
consecutive stereogenic C-atoms (these ligands also incorporate
enantiopure BINOL- or TADDOL-derived phosphites).
ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge on the
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S
General procedure for catalytic experiments, preparation
of substrates, spectral data of known and new
compounds, crystallographic data, HPLC data from
catalytic experiments (PDF)
X-ray data for syn-5 (CIF)
AUTHOR INFORMATION
Corresponding Author
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Notes
(11) For selected examples on the efficient application of P−OP
ligands bearing the TADDOL-derived phosphite in asymmetric
catalysis, see: (a) Falk, A.; Fiebig, L.; Neudoerfl, J.-M.; Adler, A.;
Schmalz, H.-G. Adv. Synth. Catal. 2011, 353, 3357−3362. (b) Naeemi,
Q.; Dindaroglu, M.; Kranz, D. P.; Velder, J.; Schmalz, H.-G. Eur. J. Org.
Chem. 2012, 2012, 1179−1185. (c) Dindaroglu, M.; Akyol, S.; Simsir,
H.; Neudorfl, J.-M.; Burke, A.; Schmalz, H.-G. Tetrahedron: Asymmetry
2013, 24, 657−662. (d) Falk, A.; Goederz, A.-L.; Schmalz, H.-G.
Angew. Chem., Int. Ed. 2013, 52, 1576−1580. (e) Falk, A.; Cavalieri, A.;
Nichol, G. S.; Vogt, D.; Schmalz, H.-G. Adv. Synth. Catal. 2015, 357,
3317−3320.
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
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We thank MINECO (CTQ2014-60256-P and Severo Ochoa
Excellence Accreditation SEV-2013-0319), the ICIQ Founda-
tion for financial support, Dr. J. Benet-Buchholz and Dr. E.
Martin for the X-ray crystallographic analysis of syn-5, and B.
Balakrishna for his generous gift of ligands L13 and L14. J.-R.
L. thanks the ICIQ Foundation for a predoctoral fellowship.
(12) For the preparation of ligands L13 and L14, see: Balakrishna, B.;
́
Bauza, A.; Frontera, A.; Vidal-Ferran, A. Chem.−Eur. J. 2016,
REFERENCES
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