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Volumn 71, Issue 5, 2006, Pages 2064-2070

Very mild, enantioselective synthesis of propargylamines catalyzed by copper(I)-bisimine complexes

Author keywords

[No Author keywords available]

Indexed keywords

ALKYLACETYLENES; CHIRAL LIGANDS; REACTION CONDITIONS;

EID: 33644656759     PISSN: 00223263     EISSN: None     Source Type: Journal    
DOI: 10.1021/jo052481g     Document Type: Article
Times cited : (120)

References (61)
  • 7
    • 0038106171 scopus 로고    scopus 로고
    • For the addition of organometallic reagents to chiral imines, see: Bloch, R. Chem. Rev. 1998, 98, 1407.
    • (1998) Chem. Rev. , vol.98 , pp. 1407
    • Bloch, R.1
  • 11
    • 0001751065 scopus 로고    scopus 로고
    • For a few selected examples of interesting methodologies affording racemic compounds, see also: Fischer, C.; Carreira, E. M. Org. Lett. 2001, 3, 4319.
    • (2001) Org. Lett. , vol.3 , pp. 4319
    • Fischer, C.1    Carreira, E.M.2
  • 44
    • 22244487956 scopus 로고    scopus 로고
    • We have recently found that the arylacetylene addition to imines is promoted also by chiral diamine/Cu(I) complexes. See: Orlandi, S.; Colombo, F.; Benaglia, M. Synthesis 2005, 1689-1691. The bisimine/Cu(I) catalysts usually performed better than diamine/Cu(I) complexes in terms of yields and stereoselectivities.
    • (2005) Synthesis , pp. 1689-1691
    • Orlandi, S.1    Colombo, F.2    Benaglia, M.3
  • 45
    • 0034624411 scopus 로고    scopus 로고
    • Reetz, M. T.; Haderlein, G.; Angermund, K. J. Am. Chem. Soc. 2000, 122, 996. Following the reported procedure, in our hands, product 9 was obtained in 51% yield after chromatographic purification.
    • (2000) J. Am. Chem. Soc. , vol.122 , pp. 996
    • Reetz, M.T.1    Haderlein, G.2    Angermund, K.3
  • 46
    • 33644641615 scopus 로고    scopus 로고
    • note
    • The use of other, even more hindered, ligands like a chiral bisimine derived from 2-hydroxy-3-t-butyl-benzaldehyde did not allow the improvement of the enantioselectivity, which was always in a 70-80% ee range. See also ref 29.
  • 47
    • 33644655071 scopus 로고    scopus 로고
    • manuscript in preparation
    • On the contrary, in a chiral bisimine/metal catalyzed allylation of imines, we have recently discovered a positive effect of the thiophene ring on the stereoselectivity of the process. See: Colombo, F.; Benaglia, M.; Cozzi, F.; Cinquini, M. manuscript in preparation.
    • Colombo, F.1    Benaglia, M.2    Cozzi, F.3    Cinquini, M.4
  • 48
    • 33644642791 scopus 로고    scopus 로고
    • note
    • In the case of product 11, it was possible to obtain a basically enantiomerically pure compound after a single crystallization step even starting from a sample with 65% ee.
  • 49
    • 33644647584 scopus 로고    scopus 로고
    • note
    • Other ligands were less efficient; for example, with ligand 1, after 48 h, less than 60% conversion was observed. Furthermore, because with other substrates and different acetylenic reagents different reaction rates were observed, for the sake of comparison, a 72 h reaction time was kept in all the experiments.
  • 50
    • 33644660336 scopus 로고    scopus 로고
    • note
    • At 0 °C, other ligands, like 2, 5, and 6, did not promote the reaction at all.
  • 51
    • 33644651684 scopus 로고    scopus 로고
    • note
    • 11 do use CuBr as the Cu(I) source, but it is complexed with Quinap or other related biaryl P,N ligands, and the reaction is believed to proceed through a different mechanism that involves an enamine formation.
  • 52
    • 33644647732 scopus 로고    scopus 로고
    • note
    • Any attempt to obtain crystals of the chiral bisimine/copper(I) complex was unsuccessful. For the proposed reaction mechanism, we do have NMR evidence of Cu(I)-imine coordination. Then the formation of a Cu-alkynide, as suggested by one of the referees, is a possibility. However, on the basis of our own investigation, at the moment we are not in the position to indicate the structure of the real active catalytic species and to assign the geometry at the copper ion.
  • 53
    • 33644654704 scopus 로고    scopus 로고
    • note
    • Imines derived from heteroaromatic aldehydes reacted sluggishly and with low enantioselectivity; imines derived from cinnamic aldehyde and aliphatic aldehydes did not react at all, as well as N-alkyl imines. N-phenyl imine of ethylglyoxalate was completely consumed after only 12 h of reaction, but any attempt to isolate a well-defined product was unsuccessful.
  • 54
    • 33644656490 scopus 로고    scopus 로고
    • note
    • For the degradation of N-2-methoxyphenyl anilines, see ref 7.
  • 55
    • 33644661230 scopus 로고    scopus 로고
    • note
    • 2). These results match with those reported in the recent paper by Li et al. (ref 8), where the absolute configuration of N-[1-(3-bromophenyl)-3-phenyl-2- propynyl]-aniline was determined by X-ray crystallography.
  • 56
    • 33644655621 scopus 로고    scopus 로고
    • note
    • Only very recently have alkylacetylenes been employed in a direct addition to imines (see ref 8). For other examples of the use of alkylacetylenes in other methodologies, see refs 9 and 7.
  • 59
    • 33644658439 scopus 로고    scopus 로고
    • note
    • The enantiomerically enriched propargylamines 11, 21-29, 35-39, and 41-44 all showed positive optical rotation values.


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.