Preparation of enamides via palladium-catalyzed amidation of enol tosylates

Organic Letters

Volumn 7, Issue 6, 2005, Pages 1185-1188

  Klapars, Artis ^a   Campos, Kevin R ^a   Chen, Cheng Yi ^a   Volante, Ralph P ^a  

^a MERCK RESEARCH LABORATORIES   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

AMIDE; ENAMINE; LIGAND; PALLADIUM; TOLUENESULFONIC ACID DERIVATIVE;

AMIDATION; ARTICLE; BIOLISTIC TRANSFORMATION; CATALYSIS; CATALYST; CROSS COUPLING REACTION; ENERGY YIELD; MOLECULAR INTERACTION; REACTION ANALYSIS; SCREENING TEST; STRUCTURE ANALYSIS; SYNTHESIS;

AMIDES; COMBINATORIAL CHEMISTRY TECHNIQUES; MOLECULAR STRUCTURE; PALLADIUM; TOSYL COMPOUNDS;

EID: 18244388691     PISSN: 15237060     EISSN: None     Source Type: Journal    
DOI: 10.1021/ol050117y     Document Type: Article

References (32)

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18. Presumably, the thermodynamic enolates were generated.
19. TsCl caused α-chlorination of the enolates.
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22. 2 in the case of Xphos. It is conceivable that the activity of these catalysts suffered as the result.
23. Use of the BINAP ligand for aryl amination: (a) Wolfe, J. P.; Wagaw, S.; Buchwald, S. L. J. Am. Chem. Soc. 1996, 118, 7215. Use of the dppf ligand for aryl amination: (b) Driver, M. S.; Hartwig, J. F. J. Am. Chem. Soc. 1996, 118, 7217.
24. Use of the BINAP ligand for aryl amination: (a) Wolfe, J. P.; Wagaw, S.; Buchwald, S. L. J. Am. Chem. Soc. 1996, 118, 7215. Use of the dppf ligand for aryl amination: (b) Driver, M. S.; Hartwig, J. F. J. Am. Chem. Soc. 1996, 118, 7217.
25. The dipf ligand has been used for a Pd-catalyzed α-arylation of a nitrile: (a) Culkin, D. A.; Hartwig, J. F. J. Am. Chem. Soc. 2002, 124, 9330. For the use of the DtBPF ligand (8) in a C-N coupling reaction. see: (b) Hamann, B. C.; Hartwig, J. F. J. Am. Chem. Soc. 1998, 120, 7369.
26. The dipf ligand has been used for a Pd-catalyzed α-arylation of a nitrile: (a) Culkin, D. A.; Hartwig, J. F. J. Am. Chem. Soc. 2002, 124, 9330. For the use of the DtBPF ligand (8) in a C-N coupling reaction. see: (b) Hamann, B. C.; Hartwig, J. F. J. Am. Chem. Soc. 1998, 120, 7369.
27. 3 and the ligand were omitted, <0.1 % yield of the desired enamide product was observed.
28. Interestingly, enol triflates exhibit a similar reactivity pattern in the Pd-catalyzed amidation reaction (see ref 5).
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31. If 1 equiv of 5-bromo-m-xylene was added to the coupling reaction of enol tosylate 1 shown in Table 1 (using ligand 9), only 35% conversion of enol tosylate and 32% conversion of aryl bromide was observed. For comparison, >99% conversion of enol tosylate was obtained in the absence of the aryl bromide.
32. 2, tert-Amyl alcohol (2.0 mL) was added via syringe, the Schlenk tube was sealed, and the reaction mixture was stirred at 80-100°C for 5-20 h. The resulting suspension was filtered through a plug of silica gel, the filtrate was concentrated, and the residue was purified by flash chromatography on silica gel to provide the desired enamide product.