Influence of copper(II) acetate on Ni/AcOH-promoted 5-endo and 5-exo radical cyclisations of trichloroacetamides

Synlett

Volumn , Issue 4, 2000, Pages 471-474

  Cassayre, Jérôme ^a   Dauge, Delphine ^a   Zard, Samir Z ^a,b  

^a CNRS   (France)

^b LABORATOIRE DE SYNTHÈSE ORGANIQUE   (France)

Author keywords

5 endo radical cyclisation; 5 exo radical cyclisation; Cu(OAc)2; Nickel; Trichloroacetamide

Indexed keywords

ACETAMIDE; COPPER ACETATE; COPPER DERIVATIVE; NICKEL; OXIDIZING AGENT;

ARTICLE; CHEMICAL STRUCTURE; CYCLIZATION; OXIDATION; OXIDATION REDUCTION REACTION; REACTION ANALYSIS;

EID: 0034127044     PISSN: 09365214     EISSN: None     Source Type: Journal    
DOI: None     Document Type: Article

References (21)

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11. +), 391, 310, 293, 276.
12. 3SnH promoted cyclisations, see ref. 7 and: Ishibashi, H.; Higuchi, M.; Ohba, M.; Ikeda, M. Tetrahedron Lett. 1998, 39, 75-78.
13. Compound 4 could also be derived in principle from 5-endo cyclisation followed by double elimination of HCl, but this possibility was rejected since the formation of the cyclised enamide was also observed starting from 2-substituted trichloroacetenamides. Ionic elimination of HCl cannot occur in these cases; the cyclic enamides must therefore be formed by oxidation of tertiary radical arising from the 5-endo ring closure, presumably by electron transfer to the starting material; see ref. 3b.
14. 4 (Cobas, A.; Guitian, E.; Castedo, L. J. Org. Chem. 1993, 58, 3113-3117). In the case of 9b (52%) and 9c (6%), the yield was lowered by the competitive formation of the C-acylated products. Surprisingly, starting from cyclooctanone, formation of 12 was found to be exclusive. For related observations, see : Morimoto, T.; Sekiya, M. Chem. Pharm. Bull. 1977, 25, 1230-1236.
15. Snider, B. B. Chem. Rev. 1996, 96, 339-363.
16. Allylic haloacetamides were generally obtained by acylation of the corresponding allylic amines, except for 13c and 13d which were prepared by Overman rearrangement of the trichloroacetimidate derived from 3-methyl-2-cyclohexen-1-ol according to: Nishikawa, T.; Asai, M.; Ohyabu, N.; Isobe, M. J. Org. Chem. 1998, 63, 188-192. The latter method is of particular interest for asymmetric synthesis since allylic alcohols are easily available in enantiomerically pure form.
17. Alternatively, it has been reported that palladium-mediated cyclisations of allylic bromo-or iodo-acetamides afford similar compounds in poor to modest yields, see: (a) Mon, M.; Kanda, N.; Oda, I.; Ban, Y. Tetrahedron 1985, 41, 5465-5474.
18. (b) Yang, S.-C; Tseng, F.-H.; Hung, C.-W. J. Chin. Chem. Soc. 1999, 46, 211-214.
19. For a study of the influence of the nitrogen substituent on 5-exo radical cyclisations of allylic trichloroacetamides, see: Nagashima, H.; Ozaki, N.; Ishii, M.; Seki, K.; Washiyama, M.; Itoh, K. J. Org. Chem. 1993, 58, 464-470.
20. Similar chlorine atom transfer reactions during Ni-induced radical cyclisations have already been observed, see ref. 2.
21. Organocopper(III) intermediates derived from primary radicals are known to interact quite easily with internal or external nucleophiles, see ref. 12.