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Volumn 69, Issue 6, 2004, Pages 1903-1908

Michael Reactions of Pseudoephedrine Amide Enolates: Effect of LiCl on Syn/Anti Selectivity

Author keywords

[No Author keywords available]

Indexed keywords

LITHIUM COMPOUNDS; NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY; REDUCTION; STEREOCHEMISTRY;

EID: 1642358493     PISSN: 00223263     EISSN: None     Source Type: Journal    
DOI: 10.1021/jo035564a     Document Type: Article
Times cited : (37)

References (37)
  • 14
    • 1642367602 scopus 로고    scopus 로고
    • note
    • Enolates of glycinamides exhibited lower selectivity in the absence of LiCl. See ref 1c.
  • 23
    • 0034826462 scopus 로고    scopus 로고
    • While this work was in progress, Myers et al. reported the conjugate addition of the lithium enolate derived from pseudoephedrine α-fluoroacetamide to a nitroalkene and vinyl sulfoxide with modest selectivities and yields. See: Myers, A. G.; Barbay, J. K.; Zhong, B. J. Am. Chem. Soc. 2001, 123, 7207-7219.
    • (2001) J. Am. Chem. Soc. , vol.123 , pp. 7207-7219
    • Myers, A.G.1    Barbay, J.K.2    Zhong, B.3
  • 24
    • 1642352923 scopus 로고    scopus 로고
    • note
    • In contrast, the alkylation requires the presence of 6 equiv of LiCl to increase conversion and the rate of alkylation. See ref 1b.
  • 28
    • 0000877113 scopus 로고
    • We found that the presence of 5-10 mol % water is crucial for reproducibility. See: Sunitha, K.; Balasubramanian, K. K. Tetrahedron 1987, 43, 3269-3278.
    • (1987) Tetrahedron , vol.43 , pp. 3269-3278
    • Sunitha, K.1    Balasubramanian, K.K.2
  • 29
    • 1642268488 scopus 로고    scopus 로고
    • note
    • The stereochemistry at the epimerizable stereocenter of 5 has not been determined.
  • 31
    • 0001161387 scopus 로고
    • A reversal in the facial selectivity in the alkylation of prolinol amide enolates with alkyl halides and epoxides was observed by Askin et al., who proposed that the lithium alkoxide of the auxiliary directs the approach of the epoxide to rationalize this observation. See: Askin, D.; Volante, R. P.; Ryan, K. M.; Reamer, R. A.; Shinkai, I. Tetrahedron Lett. 1988, 29, 4245-4248.
    • (1988) Tetrahedron Lett. , vol.29 , pp. 4245-4248
    • Askin, D.1    Volante, R.P.2    Ryan, K.M.3    Reamer, R.A.4    Shinkai, I.5
  • 32
    • 1642346394 scopus 로고    scopus 로고
    • note
    • Synclinal orientation of the Michael acceptor is considered on the basis of analogy to the stereochemical rationale proposed by Oare et al. for the addition of lithium enolates of amides and thioamides to α,β -unsaturated ketones (ref 16). The formation of anti-3 through an open transition state E is also possible.
  • 33
    • 1642320498 scopus 로고    scopus 로고
    • note
    • Although the 3,4-difluoro analogue 1c was examined as well, and generated similar results, a single representative reaction using 1a will be our focus.
  • 34
    • 1642393493 scopus 로고    scopus 로고
    • note
    • 1H spectrum revealed that the remaining portion of the reaction is made up of broadened species which may be attributed to partial aggregation.
  • 35
    • 84990085779 scopus 로고
    • For a review on the structure and reactivity of lithium enolates, see: Seebach, D. Angew. Chem., Int. Ed. Engl. 1988, 27, 1624-1654.
    • (1988) Angew. Chem., Int. Ed. Engl. , vol.27 , pp. 1624-1654
    • Seebach, D.1


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.