Nucleophilic Metal Complexes as Acylation Catalysts: Solvent-dependent Switch Mechanisms Leading to the First Catalyzed Staudinger Reaction

Organic Letters

Volumn 1, Issue 12, 1999, Pages 1985-1988

  Wack, Harald ^a   Drury III, William J ^a   Taggi, Andrew E ^a   Ferraris, Dana ^a   Lectka, Thomas ^a  

^a JOHNS HOPKINS UNIVERSITY   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

COBALT; DYES, REAGENTS, INDICATORS, MARKERS AND BUFFERS; LACTAM; ORGANOMETALLIC COMPOUND; SODIUM; SOLVENT;

ACYLATION; ARTICLE; CATALYSIS; SYNTHESIS;

ACYLATION; CATALYSIS; COBALT; INDICATORS AND REAGENTS; LACTAMS; ORGANOMETALLIC COMPOUNDS; SODIUM; SOLVENTS;

EID: 0033576424     PISSN: 15237060     EISSN: None     Source Type: Journal    
DOI: 10.1021/ol9903234     Document Type: Article

References (30)

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2. We have previously reported a novel reaction pathway divergence in the Lewis acid-catalyzed reactions of acylaziridines, see: Ferraris, D.; Drury, III.; W. J.; Cox, C.; Lectka, T. J. Org. Chem. 1998, 63, 4568.
3. 4 (1) react with alkyl halides through nucleophilic displacement followed by carbonyl insertion, see: Kerr, W. J. In Encyclopedia of Reagents for Organic Synthesis; Paquette, L. A., Ed.; John Wiley & Sons: New York, 1995; p 4633. Acylcobalt intermediates react with alcohols stoichiometrically to afford esters: Tkatchenko, I. In Comprehensive Organometallic Chemistry; Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon: Oxford, 1982: Vol. 8, p 101.
4. 4 (1) react with alkyl halides through nucleophilic displacement followed by carbonyl insertion, see: Kerr, W. J. In Encyclopedia of Reagents for Organic Synthesis; Paquette, L. A., Ed.; John Wiley & Sons: New York, 1995; p 4633. Acylcobalt intermediates react with alcohols stoichiometrically to afford esters: Tkatchenko, I. In Comprehensive Organometallic Chemistry; Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon: Oxford, 1982: Vol. 8, p 101.
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9. The Staudinger reaction is believed to be a two-step process in which nucleophilic attack of an imine on a ketene is followed by ring closure of a zwitterionic intermediate. Catalysis in such reactions generally must compete with inherently high uncatalyzed reaction rates. See: (a) Lecea, B.; Arrastia, I.; Arrieta, A.; Roa, G.; Lopez, X.; Arriortua, M. I.; Ugalde, J. M.; Cossío. F. P. J. Org. Chem. 1996, 61, 3070.
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13. In the absence of base the reaction reached ∼30% conversion after 72 h. Added di-tert-butylpyridine under standard conditions did not catalyze the reaction.
14. (a) Solvent polarity scales were taken from: Reichardt, C. Solvents and Solvent Effects in Organic Chemistiy, 2nd. ed.; VCH: Weinheim, 1998.
15. rel = 1.0). Benzyl alcohol was chosen for kinetic studies for ease of HPLC and GC product analysis. Similar results were obtained for cyclopentanol, with somewhat lower overall rates; for details see the Supporting Information.
16. 1H NMR, GC, or HPLC at specified time intervals.
17. (b) α,α,α-Trifluorotoluene is commonly referred to as benzotritluoride.
18. + has been used as a catalyst in alkylation reactions: Gobbi, A.; Landini, D.; Maia, A.; Penso, M. J. Chem. Soc., Perkin Trans. 2 1996, 2505.
19. + is also a competent Lewis acid under the specified conditions.
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22. 4 was added to 1 mmol of acetic anhydride in 3 mL of BTF and the solution was refluxed 1 h. Excess reagents were removed under vacuum, and the residue was transferred into an IR cell.
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29. (b) Using catalyst 1a gave comparable results in this reaction. Upon addition of 1 equiv of 15-crown-5, the reaction was not inhibited, indicating that catalysis is primarily nucleophilic in nature.
30. 1H NMR studies on the nature of 9 were thwarted by small amounts of apparently paramagnetic impurities.