Palladium-catalyzed intermolecular coupling of aryl halides and amides

Organic Letters

Volumn 2, Issue 8, 2000, Pages 1101-1104

  Yin, Jingjun ^a   Buchwald, Stephen L ^a  

^a MASSACHUSETTS INSTITUTE OF TECHNOLOGY   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

AMIDE; HALOGEN; PALLADIUM;

ARTICLE; CATALYSIS; CHEMISTRY; GAS CHROMATOGRAPHY;

AMIDES; CATALYSIS; CHROMATOGRAPHY, GAS; HALOGENS; PALLADIUM;

EID: 0034689845     PISSN: 15237060     EISSN: None     Source Type: Journal    
DOI: 10.1021/ol005654r     Document Type: Article

References (20)

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10. (a) Kranenburg, M.; van der Burgt, Y. E. M.; Kamer, P. C. J.; van Leeuwen, P. W. N. M. Organometallics 1995, 14, 3081-3089. Previous uses of Xantphos in C-N bond-forming reactions:
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14. 3 (456 mg, 1.4 mmol). The Schlenk tube was capped with a rubber septum, evacuated, and backfilled with argon; this evacuation/ backfill sequence was repeated one additional time. Methyl 2-bromobenzoate (0.140 mL, 215 mg, 1.0 mmol) and 1,4-dioxane (1 mL) were added through the septum. The septum was replaced with a Teflon screwcap. The Schlenk tube was sealed, and the mixture was stirred at 100°C for 35 h until the starting aryl bromide had been completely consumed as judged by GC analysis. The reaction mixture was then cooled to room temperature, diluted with dichloromethane (10 mL), filtered, and concentrated in vacuo. The crude material was purified by flash chromatography on silica gel to afford 163 mg (80%) of n-(2′-carbomethoxyphenyl)-2-azetidinone as a pale yellow oil.
15. Fox, J. M.; Huang, X.; Chieffi, A.; Buchwald, S. L. J. Am. Chem. Soc. 2000, 122, 1360-1370.
16. A substantial influence of the temperature of the reaction or the mol % of catalyst employed on the efficiency of some reactions involving unactivated aryl halides or triflate was also observed. For example, when 1 mol % of Pd catalyst was used, the reactions in entries 1-3 and 7 of Table 2 gave low conversions (<15%). When the reaction in entry 3 of Table 2 was carried out at 120°C with 5 mol % of Pd catalyst, a product/ ArBr ratio of 0.20 was obtained after 19 h. The use of 2 mol % of Pd at the same temperature gave a product/ArBr ratio of 1.1 after 16 h; no further conversion was noted after an additional 26 h. However, when the temperature was lowered to 100°C. complete conversion was achieved using 2.5 mol % of catalyst after 16 h (Table 2. entry 3). These results suggest that unknown competitive processes leading to decomposition of the catalyst can occur and that changes in reaction parameters may change the relative rates of the desired and unwanted reactions.
17. Hartwig observed similar aryl group exchange processes in palladium-catalyzed aminations: (a) Hamann. B. C.; Hartwig, J. F. J. Am. Chem. Soc. 1998, 120, 3694-3703. See also:
18. (b) Kong, K.-C.; Cheng, C.-H. J. Am. Chem. Soc. 1991, 113, 6313-6315.
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