A Convenient and Expeditious Synthesis of 3-(N-Substituted) Aminocoumarins via Palladium-Catalyzed Buchwald-Hartwig Coupling Reaction

Reaction Scheme


Decarboxylative coupling of sp-sp2 carbons is possible by palladium catalyst. Employing propiolic acid as a difunctional alkyne, and using the consecutive reactions of the Sonogashira reaction and the decarboxylative coupling, unsymmetrically substituted diaryl alkynes were obtained in moderate to good yield.



Pd2(dba)3 (0.05 mmol) and 1,1�-bis(diphenylphosphino)ferrocene (0.10 mmol) aryl iodide (1.0 mmol) and propiolic acid (1) (1.0 mmol) were combined with TBAF (6.0 mmol) in a small round-bottomed flask. N-methylpyrrolidone (6.0mml) was added and the flask was sealed with a septum. The resulting mixture was placed in an oil bath at room temperature for 12 h. Then aryl bromide (1.0 mmol) was added and stirred at 90 �C for 12 h. The reaction was poured into 20 mL of saturated aqueous ammonium chloride and extracted with (3 x 20 mL) with Et2O. The combined ether extracts were washed with brine (60mL), dried over MgSO4, and filtered. The solvent was removed under vacuum, and the resulting crude product was purified by flash chromatography on silica gel.



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