Tetrameric Phosphazene Bases


Vol. 3, No. 1
Strong and Hindered Bases in Organic Synthesis
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Introduction / Phosphazene Bases / Verkade's Superbases / Traditional bases
Preservation of Reagents / Aldrich Schlenk-Type Glassware

 Phosphazene Bases Introduction / Monomeric Phosphazene Bases (P1)
Dimeric Phosphazene Bases (P2) / Tetrameric Phosphazene Bases (P4)

Tetrameric Phosphazene Bases (P4)

The two P4 phosphazene bases offered differ slightly with respect to their steric hindrance and basicity (Table 5).

Table 5. Order of Basicity for P4 Bases
Order of steric hindrance: P4-t-Oct >> P4-t-Bu
Product Number: 79422   79421
Basicity (MeCNpKBH+): 42.7   41.9

P4-t-Bu[1] 79421 and P4-t-Oct 79422, offered as 1 M solutions in hexane have several important features. They are highly sterically hindered, extremely hygroscopic, highly stable towards hydrolysis, 18 orders of magnitude more basic than DBU,[2] and already in the basicity range typical of organolithium bases. Both 79421 and 79422 are particularly suitable for deprotonation (activation) of pronucleophiles, although also deprotonations for spectroscopic investigations,[3-7] epimerisations,[8] double bond shifts,[9] b-eliminations,[9-12] and Li+ complexation (alkyl-lithium activation)[13,14] have been reported. See Table 6 for a list of our P2 bases with their properties, package size etc.

 

Table 6. Phospazene bases P4
79421
Phosphazene base P4-t-Bu solution

1-tert-Butyl-4,4,4-tris(dimethylamino)-2,2-bis[tris(dimethylamino)-
phosphoranylidenamino]-2
Λ5,4Λ5-catenadi(phosphazene)

purum, ~1.0 M in n-hexane  C22H63N13P4   Mr 633.7  [111324-04-0]  1 ml, 5 ml, 25 ml


 
79422
Phosphazene base P4-t-Oct solution

1-tert-Octyl-4,4,4-tris(dimethylamino)-2,2-bis[tris(dimethylamino)
phosphoranylidenamino]-2
Λ5,4Λ5-catenadi(phosphazene)

purum, 1.00 M ± 0.02 M in n-hexane   C26H71N13P4   Mr 689.8   [153136-05-1]   1 ml, 5 ml


 

 

Applications: These bases attract increasing interest in the field of anionic copolymerisation[13-18] and have also been utilized for solid-phase synthesis[6] related to combinatorial chemistry.[19,20] They have been reported to support alkylations,[1,21-31] Michael-additions,[15,32,33] aldol-reactions,[28,34-37], epoxide-opening,[17,19,38,39] acylations,[40] sulfonylations,[41] anionic oxy-Cope rearrangements,[42] oxidation of carbanions[37], and transition metal-induced coupling reactions.[29,43] Among the successfully converted low acidic substrates are alcohols[35,42], amides[39,41], peptides (N- and C-activation),[24] porphyrines,[4] phosphines,[26] H-phosphonates,[31] esters,[5,25,27,35] ß-alkoxyesters[21] and -lactones[23][21][8], and b, g, d-lactones,[23,30] thioesters,[40] sulfones,[3,34] episulfones,[28] benzothiazole,[21] and benzyl aryl ethers.[36] ß-Hydroxysulfones,[34] phosphonothioates,[31] enol triflates,[40] benzofuranes,[36] and subphthalocyanines[44] are thus efficiently synthesized.

 

References:

  1. For properties, purification, handling, storage, and precautions see: L. A. Paquette, "Encyclopedia of Reagents for Organic Synthesis", Wiley, 1995, Vol. 6, p. 4110.
  2. Schwesinger, R. et al., Liebigs Ann. 1996, 1055.
  3. Gais, H.-J. et al., Angew. Chem. Int. Ed. Engl. 1988, 27, 1092).
  4. Limbach, H.-H. et al., Angew. Chem. Int. Ed. Engl. 1994, 33, 2215.
  5. Melnyk, O. et al., Tetrahedron Lett. 2001, 42, 9153.
  6. Melnyk, O. et al., J. Org. Chem. 2002, 67, 526.
  7. Solladii-Cavallo, A. et al., Tetrahedron Lett. 2002, 43, 415.
  8. Kudis, S., Helmchen, G., Tetrahedron 1998, 54, 10449.
  9. Maddaluno, J. et al., J. Org. Chem. 1998, 63, 5110.
  10. Ley, S. V. et al., Tetrahedron: Asymm. 1994, 5, 2609.
  11. Ley, S. V., Mio, S., Synlett. 1996, 789.
  12. Grimme, W. et al., J. Chem. Soc. Perkin Trans. 2 1999, 1959.
  13. E_wein, B., Mvller, M., Angew. Chem. Int. Ed. Engl. 1996, 35, 623.
  14. Mvller, M. et al., Polym. Prepr. (Am. Chem. Soc., Div. Polym. Chem.) 1996, 37, 647;
    Fvrster, S., Krdmer, S., Macromolecules 1999, 32, 2783.
  15. Pietzonka, T., Seebach, D., Angew. Chem. Int. Ed. Engl. 1993, 32, 716;
    Bvrner, H. G., Heitz, W., Macromol. Chem. Phys. 1998, 199, 1815.
  16. Molenberg, A., Mvller, M., Macromol. Rapid Commun. 1994, 16, 449;
    Van Dyke, M. E., Clarson, S. J., Polym. Prepr. (Am. Chem. Soc., Div. Polym. Chem.) 1996, 37, 668;
    Van Dyke, M. E., Clarson, S. J., J. Inorg. Organomet. Polymers 1998, 8, 111;
    Hupfield, P. C., Taylor, R. G., J. Inorg. Organomet. Polymers 1999, 9, 17.
  17. Mvller, M. et al., Macromol. Rapid Commun. 1996, 17, 143;
    Mvller, M. et al., Macromol. Symp. 1996 (Intern. Symposium on Ionic Polymerization 1995), 331;
    Schlaad, H. et al., Macromolecules 2001, 34, 4302.
  18. Memeger Jr., W. et al., Macromolecules 1996, 29, 6475, 8568.
  19. Brill, W. K.-D. et al., Synlett. 1998, 1085.
  20. Wendeborn, S. et al., Synlett. 1999, 1121.
  21. Schwesinger, R., Schlemper, H., Angew. Chem. Int. Ed. Engl. 1987, 26,1167.
  22. Schwesinger, R., Nachr. Chem. Tech. Lab. 1990, 38, 1214.
  23. Pietzonka, T., Seebach, D., Chem. Ber. 1991, 124, 1837.
  24. Pietzonka, T., Seebach, D., Angew. Chem. 1992, 104, 1543;
  25. Seebach, D. et al., Helv. Chim. Acta 1996, 79, 588.
  26. Prinzbach, H. et al., J. Am. Chem. Soc. 1993, 115, 7173.
  27. Uhlig, F. et al., Phosphorus, Sulfur & Silicon 1993, 81, 155;
    Uhlig, F. et al., Phosphorus, Sulfur & Silicon 1993, 84, 181.
  28. Solladii-Cavallo, A. et al., J. Org. Chem. 1994, 59, 5343.
  29. Muccioli, A. B., Simpkins, N. S., J. Org. Chem. 1994, 59, 5141-5143;
    Simpkins, N. S. et al., J. Chem. Soc. Perkin Trans. 1 1997, 323.
  30. Fuji, K. et al., J. Chem. Soc. Chem. Commun. 1999, 2289.
  31. Hultin, P. G. et al., Tetrahedron 1996, 52, 8685.
  32. Mioskowski, C. et al., Chem. Eur. J. 2002, 8, 2910.
  33. Bloch, R. et al., Tetrahedron: Asymm. 1997, 8, 3665.
  34. Chang, C. K. et al., Tetrahedron Lett. 1995, 36, 6408.
  35. Solladii-Cavallo, A. et al., J. Org. Chem. 1996, 61, 2690.
  36. Prinzbach, H. et al., J. Org. Chem. 2001, 66, 5744.
  37. Verkade, J. G. et al., Org. Lett. 2000, 2, 2409 (Aldol mit Benzylanion).
  38. Motorina, I. A., Grierson, D. S., Tetrahedron Lett. 1999, 40, 7211.
  39. Brill, W. K.-D., Tirefort, D., Tetrahedron Lett. 1998, 38, 787.
  40. Spaltenstein, A. et al., Bioorg. Med. Chem. Lett. 2000, 10, 1159.
  41. O4Neil, I. A. et al., Synlett. 1995, 151.
  42. Ellis, D., Tetrahedron Asymm. 2001, 12, 1589.
  43. Mamdani, H. T., Hartley, R. C., Tetrahedron Lett. 2000, 41, 747.
  44. Palomo, C. et al., J. Chem. Soc. Chem. Commun. 1998, 2091.
  45. Hanack, M. et al., Synthesis 1996, 1139.