A Practical Synthesis of Rhodium Precatalysts for Enantioselective Hydrogenative Transformations

Abstract

Herein is described a practical method of preparing enantiopure rhodium(I) complexes that can be used as efficient catalysts for the asymmetric hydrogenation of functionalized alkenes, the hydrogenative kinetic resolution of vinyl sulfoxides, and the desymmetrization of meso-dienes. All these rhodium precatalysts incorporate enantiopure phosphine–phosphite (P–OP) ligands as stereochemical directors of the hydrogenative transformations. The synthetic route starts with the ring-opening of an enantiopure Sharpless epoxy ether with a phosphorus nucleophile followed by isolation of the borane-protected phosphino alcohol derivative by crystallization. The subsequent cleavage of this borane complex, the O-phosphorylation of the resulting phosphino alcohol with the corresponding phosphorus electrophiles (chlorophosphite derivatives), and finally the complexation of the in situ generated P–OP ligands with [Rh(nbd)₂]BF₄, followed by crystallization, rendered the target precatalysts.

Key words

asymmetric hydrogenation - kinetic resolution - hydrogenative desymmetrization - phosphine–phosphite - rhodium catalysts - practical synthesis

• References


See for example:
• 1a Asymmetric Catalysis on Industrial Scale: Challenges, Approaches and Solutions. 1st ed., Blaser HU, Schmidt E. Wiley-VCH; Weinheim: 2004
• 1b Blaser H.-U, Pugin B, Spindler F, Thommen M. Acc. Chem. Res. 2007; 40: 1240
• 1c Nugent TC, El-Shazly M. Adv. Synth. Catal. 2010; 352: 753
• 1d Busacca CA, Fandrick DR, Song JJ, Senanayake CH. Adv. Synth. Catal. 2011; 353: 1825
• 1e Ager DJ, de Vries AH. M, de Vries JG. Chem. Soc. Rev. 2012; 41: 3340
• 1f Etayo P, Vidal-Ferran A. Chem. Soc. Rev. 2013; 42: 728

See for example:
• 2a Phosphorus Ligands in Asymmetric Catalysis . 1st ed., Vol. I-III, Börner A. Wiley-VCH; Weinheim: 2008
• 2b Fernández-Pérez H, Etayo P, Panossian A, Vidal-Ferran A. Chem. Rev. 2011; 111: 2119

See for example:
• 3a Handbook of Homogeneous Hydrogenation . 1st ed., Vol. I-III, de Vries JG, Elsevier CJ. Wiley-VCH; Weinheim: 2007
• 3b Wang D.-S, Chen Q.-A, Lu S.-M, Zhou Y.-G. Chem. Rev. 2012; 112: 2557
• 3c Xie J.-H, Zhu S.-F, Zhou Q.-L. Chem. Soc. Rev. 2012; 41: 4126
• 3d Hopmann KH, Bayer A. Coord. Chem. Rev. 2014; 268: 59
• 4 Fernández-Pérez H, Etayo P, Núñez-Rico JL, Balakrishna B, Vidal-Ferran A. RSC Adv. 2014; 4: 58440
• 5 We have simplified the discussion by indicating only the reagents required for synthesizing the rhodium complexes, whose synthesis has been published (i.e., the antecedents of complexes 4a and 4b). The reader is referred to the original publications (ref. 6) for the exact reaction conditions employed for a particular P–OP ligand.
• 6a Fernández-Pérez H, Donald SM. A, Munslow IJ, Benet-Buchholz J, Maseras F, Vidal-Ferran A. Chem. Eur. J. 2010; 16: 6495
• 6b Panossian A, Fernández-Pérez H, Popa D, Vidal-Ferran A. Tetrahedron: Asymmetry 2010; 21: 2281
• 6c Etayo P, Núñez-Rico JL, Fernández-Pérez H, Vidal-Ferran A. Chem. Eur. J. 2011; 17: 13978
• 6d Etayo P, Núñez-Rico JL, Vidal-Ferran A. Organometallics 2011; 30: 6718
• 6e Núñez-Rico JL, Etayo P, Fernández-Pérez H, Vidal-Ferran A. Adv. Synth. Catal. 2012; 354: 3025
• 6f Fernández-Pérez H, Benet-Buchholz J, Vidal-Ferran A. Org. Lett. 2013; 15: 3634
• 6g Fernández-Pérez H, Benet-Buchholz J, Vidal-Ferran A. Chem. Eur. J. 2014; 20: 15375
• 6h Lao JR, Benet-Buchholz J, Vidal-Ferran A. Organometallics 2014; 33: 2960
• 7 Lao JR, Fernández-Pérez H, Vidal-Ferran A. Org. Lett. 2015; 17: 4114
• 8 Manuscript in preparation.
• 9a It has been reported that O-phosphorylations employing the chlorophosphite derived from [(4S,5S)-2,2-dimethyl-1,3-dioxolane-4,5-diyl]bis(diphenylmethanol) are not so favored as those involving chlorophosphites from [1,1′-biaryl]-2,2′-diols and require a large excess of base.
• 9b See for example: Kranich R, Eis K, Geis O, Mühle S, Bats JW, Schmalz H.-G. Chem. Eur. J. 2000; 6: 2874
• 10 The required chlorophosphite was prepared following the procedure indicated in: Scherer J, Huttner G, Buechner M, Bakos J. J. Organomet. Chem. 1996; 520: 45
• 11 The required chlorophosphite was prepared following the procedure indicated in: Chikkali SH, Bellini R, de Bruin B, van der Vlugt JI, Reek JN. H. J. Am. Chem. Soc. 2012; 134: 6607
• 12 The required chlorophosphite was prepared following the procedure indicated in: Wassenaar J, de Bruin B, Reek JN. H. Organometallics 2010; 29: 2767