A Mild Amide to Carbamate Transformation

Journal of Organic Chemistry

Volumn 62, Issue 20, 1997, Pages 7054-7057

  Burk, Mark J ^a,b   Allen, John G ^a  

^a DUKE UNIVERSITY   (United States)

^b Chiroscience Ltd   (United Kingdom)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 0001701976     PISSN: 00223263     EISSN: None     Source Type: Journal    
DOI: 10.1021/jo970903j     Document Type: Article

References (23)

1. Green, T. W.; Wuts, P. G. M. Protective Groups in Organic Synthesis, 2nd ed.; Wiley: New York, 1991; p 351, 355.
2. McCulloch, B.; Halpern, J.; Thompson, M. R.; Landis, C. R. Organometallics 1990, 9, 1392.
3. (a) Burk, M. J.; Feaster, J. E.; Nugent, W. A.; Harlow, R. L. J. Am. Chem. Soc. 1993, 115, 10125.
4. (b)Burk, M. J.; Gross, M. F.; Harper, G. P.; Kalberg, C. S.; Lee, J. R.; Martinez, J. P. Pure Appl. Chem. 1996, 68, 37.
5. (a) Burk, M. J.; Gross, M. F.; Martinez, J. P. J. Am. Chem. Soc., 1995, 117, 9375.
6. (b) Burk, M. J.; Gross, M. F.; Martinez, J. P.; Straub, J. A. Manuscript in preparation.
7. Dilbeck, G. A.; Field, L.; Gallo, A. A.; Gargiulo, R. J. J. Org. Chem. 1978, 43, 4593.
8. (a) Grehn, L.; Gunnarsson, K.; Ragnarsson, U. J. Chem. Soc., Chem. Commun. 1985, 1317.
9. (b) Grehn, L.; Gunnarsson, K.; Ragnarsson, U. Acta Chem. Scand. 1986, B40, 745.
10. Flynn, D. L.; Zelle, R. E.; Greico, P. A. J. Org. Chem. 1983, 48, 2424.
11. Green, T. W.; Wuts, P. G. M. Protective Groups in Organic Synthesis, 2nd ed.; Wiley: New York, 1991; pp 327-330.
12. Grehn et al. (J. Chem. Soc., Chem. Commun. 1985, 1317) reported that the dicarbonate was required for acylation, rather than the chloroformate or other acylating reagent. This result was confirmed in the current study.
13. 2O gave 80% and 90% completion, respectively.
14. Free amine formed during the reactions would have been lost during the workup. Its formation however was unlikely due to the stability of amides and carbamates to the reaction conditions.
15. After 4 h ethanolamine, 20.3% conversion, 2.0% 1, 17.6% 3, ethylenediamine; 43.5% conversion, 2.9% 1, 42.8% 3.
16. Carey, F. A.; Sundberg, R. J. Advanced Organic Chemistry Part A: Structure and Mechanisms, 2nd ed.; Plenum: New York, 1991; p 228.
17. NaOMe was used (18 h, rt, MeOH) to intentionally racemize the amino acid in the reaction 2 to 3 for comparison to the chiral products. In these reactions, racemization was faster than acetamide cleavage. Cleavage of the carbamate was also detected. Racemic DLvaline was also purchased and derivatized for comparison. (15) 0.3% of the enantiomer was detected.
18. Substrates for compounds 4 and 5 were obtained in >99% ee and 98.9% ee, respectively, using (R,R)-PrDuPHOS-Rh and (R,R)EtDuPHOS-Rh (see ref 4a). Substrates for compounds 6, 7, and 8 were obtained in 96.9% ee and 95.9% ee and 97.4% ee, respectively, using (R,R)-MeBPE-Rh, (S,S)-MeBPE-Rh, (R,R)-MeBPE-Rh (see ref 5a).
19. Substrate for compound 9 obtained in 96.6% ee by the use of (S,S)-MeDuPHOS-Rh. See: Burk, M. J.; Allen, J. A.; Kiesrnan, W. F. Manuscript in preparation.
20. For a review, see: Gawley, R. E. Org. React. 1988, 35, 1.
21. For a review, see: Krimen, L. I.; Cota, D. J. Org. React. 1969, 17, 213.
22. 2U) gave only dibenzyl carbonate, the product of catalytic decomposition of the reagent by benzyl oxide released by the first acylation event. Trapping agents did not improve the reaction. In an effort to use a bulkier leaving group, the mixed dicarbonate benzyl tert-butyl dicarbonate (14) was prepared from sodium tert-butoxide, carbon dioxide, and benzyl chloroformate. Acylation of O-acetyl-Nbenzoyl-L-serine benzyl ester gave a 4:1 mixture of the Cbz imide to the Boc imide. Please see Supporting Information.
23. All GC samples were of crude material before purification by column chromatography.