Alkynylation of Aryl Bromides with Propargylamines Catalyzed by a Palladium-Tetraphosphine Complex

The tetraphosphine all-cis-1,2,3,4-tetrakis(diphenylphosphinomethyl)cyclopentane in combination with [Pd(C3H5)Cl]2 affords a very efficient catalyst for the alkynylation of aryl bromides with propargylamines. Higher reactions rates were observed with N,N-dialkylpropargylamines than with N-methylpropargylamine or propargylamine. A wide variety of substituents such as alkyl, phenyl, methoxy, dimethylamino, fluoro, trifluoromethyl, acetyl, benzoyl, formyl, carboxylate, nitro, or nitrile, on the aryl bromides are tolerated. High turnover numbers can be obtained with most of these aryl bromides. The coupling reaction of sterically very congested aryl bromides such as 9-bromoanthracene or 2,4,6-triisopropylbromobenzene also proceeds in good yields.