Cationic palladium complexes alkyne carbonylation

Drent, E. Amoldy, P. Budzelaar, P.H.M. (1994) Homogeneous catalysis by cationic palladium complexes - precision catalysis in the carbonylation of alkynes, J. Organomet. Chem., 415, 57-63. 

The discovery of the above-mentioned class of highly efficient alkyne carbonylation catalysts originated from a general study of reactions homogeneously catalyzed by cationic metal complexes [6, 8, 9], e. g., the methoxycarbonylation of propyne (eq. (2)). The catalysts applied were cationic palladium phosphine systems prepared in situ from three components (1) palladium acetate, (2) an excess (10-40-fold on Pd) of a (mono)phosphine ligand(L) and (3) an acid (HX) [8]. Methanol was used as both reactant and solvent, but many other solvents can also be used, such as A-methyl-2-pyrrolidone (NMP) or product MMA. 

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