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DOI: 10.1039/A703936K (Paper) Reference Section for: J. Chem. Soc., Perkin Trans. 1, 1997, 3509-3518

Synthesis of chiral β-aminophosphine oxides via novel azaboretidinium bromide salts[hair space]1

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Brian L. Booth, Nicholas J. Lawrence and Humayan S. Rashid

Abstract

The enamino(triphenyl)phosphonium salts [Ph3PCH[double bond, length half m-dash]CMeNR1R2]+ Br– [where R1 = R2 = (CH2)4, (CH2)5; (S)-CHMePh; R1 = H, R2 = (S)-CHMePh; R1 = H, R2 = (S)-(C>>|  >>H2)3-C>>|  >>H(CH2OH)] have been synthesised and have been shown to react with an excess of borane·tetrahydrofuran to give novel azaboretidinium salts—the first examples of four-membered C–B–N–C heterocycles. The structure of [(1S,3R,4S,1′S)-4-methyl-1-(1-phenylethyl)-1,2-azaboretidin-1-ium-2-uid-3-yl]triphenylphosphonium bromide has been established by X-ray crystallography. Borane does not result in any significant stereoselectivity in these reductions and the azaboretidinium salts are mixtures of diastereomers. In contrast, the similar reduction with (R)-(+)-monoisopinocampheylborane or (S)-(–)-monoisopinocampheylborane leads to single diastereomers in high yields when R1 and R2 are non-bulky; with sterically demanding groups the azaboretidinium salts are unstable and decompose on work-up. Heating these azaboretidinium salts with aqueous sodium hydroxide in methanol, or better, aqueous sodium hydroxide alone, results in the direct formation of the phosphine oxides, Ph2P(O)CH2CHMeNR1R2 which, in the case of compounds derived from Ipc2BH2, have an ee value of >75%. In some cases, particularly when R1 and R2 are bulky, the use of sodium hydroxide in methanol results in an appreciable amount of rac-Ph2PCH2CHMe(OMe) as a by-product, but this can be avoided by carrying out the reactions in the absence of methanol.

References

  1. Part of this work has been previously reported in B. L. Booth, N. J. Lawrence, R. G. Pritchard and H. S. Rashid, J. Chem. Soc., Chem. Commun., 1995, 287 Search PubMed.
  2. G. K. Anderson and R. Kumar, Inorg. Chem., 1984, 23, 4064 CrossRef CAS.
  3. L. Dahlenburg, S. Kersten and D. Werner, J. Organomet. Chem., 1991, 411, 457 CrossRef CAS.
  4. T. J. Uriate, K. D. Tan and D. W. Meek, Inorg. Chem., 1980, 19, 79 CrossRef.
  5. L. Sacconi, C. A. Mealli and F. Zanobini, Inorg. Chem., 1975, 14, 1380 CrossRef CAS.
  6. H. Werner, A. Hampp and B. Windmüller, J. Organomet. Chem., 1992, 435, 169 CrossRef CAS.
  7. L. D. Field and I. J. Luck, Tetrahedron Lett., 1994, 35, 1109 CrossRef CAS.
  8. D. J. Collins, S.-A. Mollard, N. Rose and J. M. Swan, Aust. J. Chem., 1974, 27, 2365 CAS.
  9. H. Takahashi and K. Achiwa, Chem. Lett., 1987, 1921 CAS.
  10. W. R. Cullen, S. V. Evans, N. F. Han and J. Trotter, Inorg. Chem., 1987, 26, 514 CrossRef CAS.
  11. H. Kubota and K. Koga, Tetrahedron Lett., 1994, 35, 6689 CrossRef CAS.
  12. M. Kanai, K. Koga and K. Tomioka, Tetrahedron Lett., 1992, 33, 7193 CrossRef CAS.
  13. J. Barluenga, F. López and F. Palacios, Synthesis, 1989, 298 CrossRef CAS.
  14. V. G. Markl and B. Markl, Tetrahedron Lett., 1981, 22, 4459 CrossRef.
  15. D. Cavalla and S. Warren, Tetrahedron Lett., 1983, 24, 295 CrossRef CAS; D. Carvalla, W. B. Cruse and S. Warren, J. Chem. Soc., Perkin Trans. 1, 1987, 1883 RSC.
  16. M. I. K. Amer, B. L. Booth and P. Bitrus, J. Chem. Soc., Perkin Trans. 1, 1991, 1673 RSC.
  17. B. Beagley, P. Bitrus, B. L. Booth and R. G. Pritchard, J. Chem. Soc., Perkin Trans. 1, 1993, 1039 RSC.
  18. P. Bitrus and B. L. Booth, J. Chem. Res., 1993, 168 Search PubMed.
  19. S. DeVoe Goff, W. P. Murray and E. E. Schweizer, J. Org. Chem., 1977, 42, 200 CrossRef.
  20. M. A. Caleago and E. E. Schweizer, J. Org. Chem., 1978, 43, 4207 CrossRef.
  21. K. Eiter and H. Oegiger, Justus Liebigs Ann. Chem., 1965, 62, 682.
  22. J. Barluenga, F. López and F. Palacios, Tetrahedron Lett., 1988, 29, 4863 CrossRef CAS; J. Barluenga, F. H. Cano, M. C. Foces-Foces, F. López and F. Palacios, J. Chem. Soc., Perkin Trans. 1, 1988, 2329 RSC.
  23. F. Palacios, D. Aparicio and J. Garcia, Tetrahedron, 1996, 52, 9609 CrossRef CAS.
  24. H. J. Bestmann, P. Erlmann, H. Oechsner and G. Schmid, Chem. Ber., 1984, 117, 1561 CAS.
  25. M. B. Eleveld, H. Hogeveen and E. P. Schudde, J. Org. Chem., 1986, 51, 3635 CrossRef CAS.
  26. H. C. Brown, P. K. Jadhav and A. K. Mandal, J. Org. Chem., 1986, 51, 3635 CrossRef CAS.
  27. H. C. Brown, N. Inoue, M. W. Rathke and K. R. Varma, J. Am. Chem. Soc., 1966, 88, 2870 CrossRef.
  28. G. M. Sheldrick, in Crystallographic Computing 3, ed. G. M. Sheldrick, C. Kruger and R. Goddard, OUP, London, 1985, p. 175 Search PubMed.
  29. P. T. Beurskens, DIRDIF: Direct methods for Difference Structure—an automatic procedure for phasing extension and refinement of difference structure factors. Technical Report 1984/1, Crystallographic Laboratory, Toernooiveld, 6525 Ed. Nijmegen, Netherlands.
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