Remarkable activation of an alkyne [2+2+2]-cycloaddition catalyst, 2-iminomethylpyridine (dipimp)/CoClmiddot;6H/Zn, by a phthalate additive

Article abstract of DOI:10.1055/s-0032-1317318

A catalyst for alkyne [2+2+2]-cycloaddition reactions, 2-(2,6- diisopropylphenyl)iminomethylpyridine (dipimp)/CoClmiddot;6H/Zn, can be effectively activated by addition of a catalytic amount of dialkyl phthalate to enable reactions that cannot proceed under unactivated conditions. The activation by adding phthalate was ligand- and solvent-dependent, and it was unique to dipimp and N-methyl-2-pyrrolidone (NMP). With use of diphosphine ligand instead of dipimp or with use of tetrahydrofuran (THF) instead of NMP, no activation by a phthalate additive was observed. This simple method of catalyst activation with use of inexpensive, commercially available compounds is highly practical and may find many applications. Georg Thieme Verlag Stuttgart · New York.