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Design and Synthesis of Helically Chiral Spirocyclic P3 Phosphazenes and Characterization of Their Onium Salts
Received: 03 October 2013
Accepted: 04 October 2013
28 October 2013 (online)
Helically chiral spirocyclic P3 phosphazenes were designed as a novel family of chiral organosuperbases. The newly designed chiral P3 phosphazenes were synthesized from commercially available sources in several steps and characterized by X-ray crystallographic analysis of their onium salts. The optically pure P3 phosphazenium salt was obtained by using preparative chiral stationary phase HPLC and the absolute configuration of the helical chirality was determined.
References and Notes
- 1a Palomo C, Oiarbide M, López R. Chem. Soc. Rev. 2009; 38: 632
- 1b Superbases for Organic Synthesis . Ishikawa T. John Wiley & Sons; Chippenham: 2009
- 2a Schwesinger R, Schlemper H. Angew. Chem., Int. Ed. Engl. 1987; 26: 1167 ; and references therein
- 2b Schwesinger R, Willaredt J, Schlemper H, Keller M, Schmitt D, Fritz H. Chem. Ber. 1994; 127: 2435 ; and references therein
- 2c Schwesinger R, Schlemper H, Hasenfratz C, Willaredt J, Dambacher T, Breuer T, Ottaway C, Fletschinger M, Boele J, Fritz H, Putzas D, Rotter HW, Bordwell FG, Satish AV, Ji G.-Z, Peters E.-M, Peters K, von Schnering HG, Walz L. Liebigs Ann. 1996; 1055
- 3a Tang JS, Dopke J, Verkade JG. J. Am. Chem. Soc. 1993; 115: 5015
- 3b Kisanga PB, Verkade J, Schwesinger R. J. Org. Chem. 2000; 65: 5431
- 3c Verkade JG. Top. Curr. Chem. 2003; 223: 1 ; and references therein
- 4 Schwesinger R. Chimia 1985; 39: 269
- 5a Ishikawa T, Kumamoto T. Synthesis 2006; 737
- 5b Leow D, Tan C.-H. Chem. Asian J. 2009; 4: 488
- 5c Sohtome Y, Nagasawa K. Synlett 2010; 1
- 5d Leow D, Tan C.-H. Synlett 2010; 1589
- 5e Terada M. J. Synth. Org. Chem., Jpn. 2010; 68: 1159
- 5f Uraguchi D, Ooi T. J. Synth. Org. Chem., Jpn. 2010; 68: 1185
- 6 For the preparation of chiral phosphatrane derivatives, see: Ilankumaran P, Zhang G, Verkade JG. Heteroatom Chem. 2000; 11: 251
- 7 For the preparation of chiral P1 phosphazene derivatives, see: Köhn U, Schulz M, Schramm A, Günther W, Görls H, Schenk S, Anders E. Eur. J. Org. Chem. 2006; 4128
- 8a Bandar JS, Lambert TH. J. Am. Chem. Soc. 2012; 134: 5552
- 8b Bandar JS, Lambert TH. J. Am. Chem. Soc. 2013; 135: 11799
- 9 Takeda T, Terada M. J. Am. Chem. Soc. 2013; 135: 15306
- 10 The enantiomers of (±)-1a·HBF4 were resolved by using analytical HPLC equipped with a Daicel CHIRALPAK IB (MeOH–Et2NH = 100:0.1, 1.0 mL/min, 240 nm, 40 °C): t R = 23.3, 26.0 min. See Supporting Information (page S14).
- 11 CCDC-964338 [(±)-1a·HI] contains the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
- 12 The enantiomers of (±)-1b·HCl were resolved by using analytical HPLC equipped with a Daicel CHIRALPAK IB (MeOH–Et2NH = 100:0.1, 1.0 mL/min, 240 nm, 40 °C): t R = 29.9 (isolated), 33.5 min. See Supporting Information (page S18).
- 13 The second peak could not be isolated in an optically pure form because of overlap with the first peak under the preparative chiral stationary phase HPLC conditions.
- 14 Specific rotation of the first eluting enantiomer, (+)-1b·HCl: [α] d 27 +91.7 (c 0.90, CHCl3).
- 15 CCDC-964339 [(±)-1b·HBr] contains the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
For reviews on organobase catalysis, see:
For reviews on enantioselective catalysis by using chiral guanidines and P1 phosphazenes, see: