Synthetic Approaches to New Diastereomerically Pure Ferrocenyl Triphosphine­s Combining Phosphorus, Planar, and Carbon Chirality

Abstract

Two new diastereomeric ferrocenyl triphosphine ligands P3Chir 1 and 2 have been conveniently synthesized through a multi-step reaction sequence starting from (R)-(S)-diphenylphosphinoferrocenylamine [(R)-(S)-PPFA]. Chromatographic resolution of the diborane protected-phosphine oxide derivatives, followed by a stereoconservative­ reduction/deboronation step, gave the pure triphosphines P3Chir in which the planar chirality of the ferrocenyl unit is combined with phosphorus and carbon stereocenters in an unprecedented molecular assembly.

Key words

chiral - ferrocenes - phosphines - tridentate ligands - chromatographic resolution

References

• 1 Catalytic Asymmetric Synthesis   2nd Ed.:  Ojima I. Wiley-VCH; New York: 2000. 
• 2 For a discussion of the significance of C₂ symmetry, see: Whitesell JK. Chem. Rev.  1989,  89:  1581 
• 3a For a review, see: Hayashi T. In Ferrocenes: Homogeneous Catalysis, Organic Synthesis, Materials Science   Togni A. Hayashi T. VCH; Weinheim: 1995.  p.105-142  ; and references cited therein
• 3b First report: Hayashi T. Yamamoto K. Kumada M. Tetrahedron Lett.  1974,  4405 
• 4a Burk MJ. Harlow RL. Angew. Chem., Int. Ed. Engl.  1990,  29:  1462 
• 4b Burk MJ. Feaster JE. Harlow RL. Tetrahedron: Asymmetry  1991,  2:  569 
• 4c Ward TR. Venanzi LM. Albinati A. Lianza F. Gerfin T. Gramlich V. Ramos Tombo GM. Helv. Chim. Acta  1991,  74:  983 
• 4d Jia G. Lee HM. Williams ID. Organometallics  1996,  15:  4235 
• 4e Heidel H. Scherer J. Asam A. Huttner G. Walter O. Zsolnai L. Chem. Ber.  1995,  128:  293 
• 4f King RB. Bakos J. Hoff CD. Markó L. J. Org. Chem.  1979,  44:  3095 
• 4g Johnson CR. Imamoto T. J. Org. Chem.  1987,  52:  2170 
• 4h Lee HM. Bianchini C. Jia G. Barbaro P. Organometallics  1999,  18:  1961 
• 5 Cotton FA. Hong B. Progr. Inorg. Chem.  1992,  40:  179 
• 7a Barbaro P. Togni A. Organometallics  1995,  14:  3570 
• 7b Barbaro P. Bianchini C. Togni A. Organometallics  1997,  16:  3004 
• 7c Barbaro P. Bianchini C. Oberhauser W. Togni A. J. Mol. Cat. A: Chem.  1999,  145:  139 
• 7d Hintermann L. Perseghini M. Barbaro P. Togni A. Eur. J. Inorg. Chem.  2003,  601 
• 8 Barbaro P. Bianchini C. Giambastiani G. Togni A. Chem. Commun.  2002,  2672 
• 9a Blaser HU. Brieden W. Pugin B. Spindler F. Studer M. Togni A. Top. Catal.  2002,  19:  3 
• 9b Togni A. Breutel C. Schnyder A. Spindler F. Landert H. Tijani A. J. Am. Chem. Soc.  1994,  116:  4062 
• 10 King RB. Cloyd JC. J. Am. Chem. Soc.  1975,  97:  46 
• 11 Togni A. Breutel C. Soares MC. Zanetti N. Gerfin T. Gramlich V. Spindler F. Rihs G. Inorg. Chim. Acta  1994,  222:  213 ; and references cited therein
• 12 Tani K. Brown LD. Ahmed J. Ibers JA. Yokota M. Nakamura A. Otsuka S. J. Am. Chem. Soc.  1977,  99:  7878 
• 13 Roberts NK. Wild SB. J. Am. Chem. Soc.  1979,  101:  6254 
• 14 Ohff M. Holz J. Quirmbach M. Börner A. Synthesis  1998,  1391 
• 15 Our best eluting solvent was a mixture of CH₂Cl₂- hexane in a 1:3 ratio; neutral aluminium oxide was used as stationary phase. For details on the chromatographic procedure see: Still WC. Khan M. Mitra A. J. Org. Chem.  1978,  43:  2923 
• 16 Pietrusiewicz KM. Zablocka M. Chem. Rev.  1994,  94:  1375 
• 17 Horner L. Pure Appl. Chem.  1964,  9:  225 
• 18 Marsi KL. J. Org. Chem.  1974,  39:  265 
• 20a Horner L. Balzer WD. Tetrahedron Lett.  1965,  1157 
• 20b Naumann K. Zon G. Mislow K. J. Am. Chem. Soc.  1969,  91:  7012 
• 21a Naumann K. Zon G. Mislow K. J. Am. Chem. Soc.  1969,  91:  2788 
• 21b Naumann K. Zon G. Mislow K. J. Am. Chem. Soc.  1969,  91:  7012 
• 21c DeBruin KE. Zon G. Naumann K. Mislow K. J. Am. Chem. Soc.  1969,  91:  7027 
• 23a Imamoto T. Oshiki T. Onozawa T. Kusumoto T. Sato K. J. Am. Chem. Soc.  1990,  112:  5244 
• 23b For a review on boronation/deboronation of phosphorus, see: Ohff M. Holz J. Quirmbach M. Börner A. Synthesis  1998,  1391 
• 24 Imamoto T. Kusumoto T. Suzuki N. Sato K. J. Am. Chem. Soc.  1985,  107:  5301 
• 26 Barbaro P. Bianchini C. Giambastiani G. Togni A. Eur. J. Inorg. Chem.  2003,  in press 
• 27 Hayashi T. Mise T. Fukushima M. Kagotani M. Nagashima N. Hamada Y. Matsumoto A. Kawakami S. Konishi M. Yamamoto K. Kumada M. Bull. Chem. Soc. Jpn.  1980,  53:  1138 
• 28 Berlin KD. Butler GB. J. Am. Chem. Soc.  1961,  26:  2537 
• 29a James BR. Ochiai E. Rempel GI. Inorg. Nucl. Chem. Lett.  1971,  7:  701 
• 29b Summers MF. Marzilli LG. Bax A. J. Am. Chem. Soc.  1986,  108:  4285 
• 31 Altomare A. Burla MC. Camalli M. Cascarano G. Giacovazzo C. Guagliardi A. Polidori G. Spagna R. J. Appl. Cryst.  1999,  32:  115 
• 32 Sheldrick GM. SHELX-97. Program for Structure Refinement   University of Göttingen; Germany: 1997. 

6

(S)-(R)-Pigiphos = bis{(S)-1-[(R)-2-(diphenylphosphanyl)-ferrocenyl]ethyl}cycloexylphosphane.

19

The absolute configurations of the side-reaction products 12, 13, 14 and 15 were deducted both from the analysis of the ³¹P{¹H} NMR spectra of the reaction mixture and by comparison with the data of compounds 1, 2, 10, 11, respectively.

22

Flash chromatography on silica gel; gradient of elution: EtOAc-pentane, from 1.50:2.75 to 1: 1.

25

The oxidation of a few milligrams of 1 with an excess of H₂O₂ (30 wt%) in CHCl₃ gave the diastereopure triphosphine trioxide allowing the unambiguous assignment of the absolute configurations of the two epimers 10 and 11.

30

CCDC 184405 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/conts/retrieving.html (or from the CCDC, 12 Union Road, Cambridge CB2 1EZ, UK; fax: [phone]; e-mail: [e-mail]).

33

CCDC 184406 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/conts/retrieving.html (or from the CCDC, 12 Union Road, Cambridge CB2 1EZ, UK; fax:+ 44 1223 336033; e-mail: [e-mail]).