Efficient and expeditious protocols for the synthesis of racemic and enantiomerically pure endocyclic enecarbamates from N-acyl lactams and N-acyl pyrrolidines

Journal of Organic Chemistry

Volumn 64, Issue 18, 1999, Pages 6646-6652

  Oliveira, Denilson F ^a,b   Miranda, Paulo C M L ^a   Correia, Carlos R D ^a  

^a UNIVERSITY OF CAMPINAS   (Brazil)

^b FEDERAL UNIVERSITY OF LAVRAS   (Brazil)

Author keywords

[No Author keywords available]

Indexed keywords

CARBAMIC ACID DERIVATIVE; LACTAM DERIVATIVE; PYRROLIDINE DERIVATIVE;

ARTICLE; CHIRALITY; ENANTIOMER; REACTION ANALYSIS; STEREOCHEMISTRY; SYNTHESIS;

EID: 0032887207     PISSN: 00223263     EISSN: None     Source Type: Journal    
DOI: 10.1021/jo9903297     Document Type: Article

References (43)

1. For reviews, see: (a) Campbell, A. L.; Lenz, G. R. Synthesis 1987, 421.
2. (b) Lenz, G. R. Synthesis 1978, 489. Although these reviews focused on enamides, the authors use the term enamide in a rather broad sense including enecarbamates.
3. For some selected examples, see: (a) Bueno, A. B.; Hegedus, L. S. J. Org. Chem. 1998, 63, 684.
4. (b) Bach, T.; Brummerhop, H. Angew. Chem., Int. Ed. Engl. 1998, 37, 3400.
5. (c) Cossy, J.; Cases, M.; Pardo, D. G. Synlett 1998, 507.
6. (d) Wolf, L. B.; Tjen, K. C. M. F.; Rutjes, F. P. T.; Hiemstra, H.; Schoemaker, H. E. Tetrahedron Lett. 1998, 39, 5081.
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11. (i) Martin, S. F.; Rein, T.; Liao, Y. Tetrahedron Lett. 1991, 32, 6481.
12. In addition to refs 1 and 2, for specific references on the synthesis of enecarbamates consult the following: (a) Cossy, J.; Cases, M.; Pardo, D. G. Synth. Commun. 1997, 27, 2769.
13. (b) McDonald, F. E.; Chatterjee, A. K. Tetrahedron Lett. 1997, 38, 7687.
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24. (a) Adapted from Langlois, N.; Rojas, A. Tetrahedron 1993, 49, 77.
25. (b) See also ref 3c.
26. Adapted from the work of Choi, J. K.; Ha, D. C.; Hart, D. L.; Lee, C. S.; Ramesh, S.; Wu, S. J. Org. Chem. 1989, 54, 279. See also ref 3c.
27. Adapted from the following: (a) Altman, K. W. Tetrahedron Lett. 1993, 34, 7721.
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29. (c) Hubert, J. C.; Wijnberg, J. B. P. A.; Speckamp, W. N. Tetrahedron 1975, 31, 1437.
30. Procedure adapted from the work of Nagasaka, T.; Tamano, H.; Maekawa, T.; Hamaguchi, F. Heterocycles 1987, 26 (3), 617.
31. Yoshifuji, S.; Tanaka, K.; Kawai, T.; Nitta, Y. Chem. Pharm. Bull. 1986, 34, 3873.
32. 2EtN frequently led to the formation of side products in variable yields. Formula represented
33. This dimeric compound contains the basic skeleton of the bispiperidine alkaloid ammodendrine (see: Pinder, A. R. Nat. Prod. Rep. 1989, 515) and also the enamine form of tetrahydroanabasine (see: Koomen, G.-J.; Wanner, M. J. J. Org. Chem. 1996, 61, 5581).
34. This dimeric compound contains the basic skeleton of the bispiperidine alkaloid ammodendrine (see: Pinder, A. R. Nat. Prod. Rep. 1989, 515) and also the enamine form of tetrahydroanabasine (see: Koomen, G.-J.; Wanner, M. J. J. Org. Chem. 1996, 61, 5581).
35. 4Cl, in our hands this procedure led to low conversion of the α-methoxycarbamate, resulting in low overall yields of the corresponding enecarbamate. To ensure higher conversions, it was necessary to heat the reaction mixture for 1-2 h. It is conceivable that the longer reaction times were responsible for the degree of racemization observed, in the range of 5-10%.
36. D = -108 (c 0.71, MeOH) for compound 18b.
37. D = -101.1 (c 1.22, EtOH) for an ethyl analogue of 18b.
38. 3)
39. D value for 30c is not reported in the recent literature, we checked its enantiomeric excess (ee) by chiral phase GC. The ee found for 30c was > 98%.
40. 3CN): Coudert, E.; Acher, F.; Azerad, R. Synthesis 1997, 863.
41. 3CN): Coudert, E.; Acher, F.; Azerad, R. Synthesis 1997, 863.
42. (S)-Pyroglutamic acid was converted to (S)-5-(hydroxymethyl-2-pyrrolidinone according to the procedure described in Saijo, S.; Wada, M.; Ishida, A.; Himizu, J.-I. Chem. Pharm. Bull. 1980, 28, 1449. The hydroxy group was then protected by standard procedures as described in Colvin, E. W. Silicon Reagents in Organic Synthesis; Academic Press: London, 1988.
43. (S)-Pyroglutamic acid was converted to (S)-5-(hydroxymethyl-2-pyrrolidinone according to the procedure described in Saijo, S.; Wada, M.; Ishida, A.; Himizu, J.-I. Chem. Pharm. Bull. 1980, 28, 1449. The hydroxy group was then protected by standard procedures as described in Colvin, E. W. Silicon Reagents in Organic Synthesis; Academic Press: London, 1988.