S-(1-Oxido-2-pyridinyl)-1,1,3,3-tetramethylthiouronium Hexafluorophosphate. A New Reagent for Preparing Hindered Barton Esters

Journal of Organic Chemistry

Volumn 63, Issue 17, 1998, Pages 5732-5733

  Garner, Philip ^a   Anderson, James T ^a   Dey, Subhakar ^a   Youngs, Wiley J ^b   Galat, Kevin ^b  

^a CASE WESTERN RESERVE UNIVERSITY   (United States)

^b UNIVERSITY OF AKRON   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 0001505956     PISSN: 00223263     EISSN: None     Source Type: Journal    
DOI: 10.1021/jo980870n     Document Type: Article

References (20)

1. (a) Garner, P. P.; Cox, P. B.; Klippenstein, S. J. J. Am. Chem. Soc. 1995, 117, 4183-4184.
2. (b) Garner, P.; Leslie, R.; Anderson, J. T. J. Org. Chem. 1996, 61, 6754-6755.
3. (c) Garner, P.; Anderson, J. T. Tetrahedron Lett. 1997, 38, 6647-6650.
4. Review: Crich, D. Aldrichim. Acta 1987, 20, 35-42.
5. Others have made similar observations when preparing Barton esters. Cf. (a) Barton, D. H. R.; Crich, D.; Motherwell, W. B. Tetrahedron 1985, 41, 3901-3924 (b) Baldwin, J. E.; Molony, M. G.; North, M. Ibid. 1989, 45, 6309-6318. (c) Ziegler, F. E.; Belema, M. J. Org. Chem. 1994, 59, 7962-7967.
6. Others have made similar observations when preparing Barton esters. Cf. (a) Barton, D. H. R.; Crich, D.; Motherwell, W. B. Tetrahedron 1985, 41, 3901-3924 (b) Baldwin, J. E.; Molony, M. G.; North, M. Ibid. 1989, 45, 6309-6318. (c) Ziegler, F. E.; Belema, M. J. Org. Chem. 1994, 59, 7962-7967.
7. Others have made similar observations when preparing Barton esters. Cf. (a) Barton, D. H. R.; Crich, D.; Motherwell, W. B. Tetrahedron 1985, 41, 3901-3924 (b) Baldwin, J. E.; Molony, M. G.; North, M. Ibid. 1989, 45, 6309-6318. (c) Ziegler, F. E.; Belema, M. J. Org. Chem. 1994, 59, 7962-7967.
8. Bohne, C.; Boch, R.; Scaiano, J. C. J. Org. Chem. 1990, 55, 5414-5418.
9. For a review of available methods for Barton esterification, see: Barton, D. H. R.; Samadi, M. Tetrahedron 1992, 48, 7083-7090 and references therein.
10. HATU = O-(7-azabenzotriazol-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate. Carpino, L. A. J. Am. Chem. Soc. 1993, 115, 4397-4398.
11. TPTU = 2-(2-oxo-1(2H)-pyridyl)-1,1,3,3-tetramethyluronium tetrafluoroborate. Knorr, R.; Trzeciak, A.; Bannwarth, W.; Gillessen, D. Tetrahedron Lett. 1989, 30, 1927-1930.
12. Dourtoglou, V.; Gross, B.; Lambropoulou, V.; Zioudrou, C. Synthesis 1984, 572-574.
13. The authors have deposited the atomic coordinates and thermal parameters for compound 8 with the Cambridge Crystallographic Data Centre. The coordinates can be obtained, on request, from the Director, Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge, CB2 1EZ, UK.
14. Both HATU (X = N) and the structurally related O-(benzotriazol-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate (HBTU, X = CH) have been shown to crystallize in the guanidinium form i rather than the commonly depicted uronium form ii. See: Abdelmoty, I.; Albericio, F.; Carpino, L. A.; Foxman, B. M.; Kates, S. A. Lett. Pept. Sci. 1994, 1, 57-67. (Matrix Presented)
15. The "parent" S-(pyridine-1-oxide-2-yl)thiouronium salt is known: Shaw, E.; Bernstein, J.; Losee, K.; Lott, W. A. J. Am. Chem. Soc. 1950, 72, 4362-4364.
16. A detailed experimental may be found in the Supporting Information.
17. Crich, D.; Ritchie, T. J. Chem. Soc., Perkin Trans. 1 1990, 945-954.
18. Sugai, T.; Shen, G.-J.; Ichikawa, Y.; Wong, C.-H. J. Am. Chern. Soc. 1993, 115, 413-421.
19. Barton, D. H. R.; Togo, H.; Zard, S. Z. Tetrahedron 1985, 41, 5507-5516.
20. Barton, D. H. R.; Hervé, Y.; Potier, P.; Thierry, J. Tetrahedron 1987, 43, 4297-4308.