A Convenient Gold(I) Complex Used for the Preparation of Cationic Gold(I) Complexes

(Triphenylphosphine)gold(I) chloride (1) is an air stable monovalent gold complex and it affords active cationic gold(I) complexes (2) by the treatment with some silver salts. Recently, hydroaminations to unsaturated bonds and cycloisomerizations of enynes using 2 as an active species have been reported, and it is showed that the reactivity of 2 is often different based on the different silver salts used in the preparation of 2. Cationic gold(I) complexes (2) prepared from AgBF₄ or AgSbF₆ salts are generally unstable due to the fluorine-based counterion. Therefore, they are promptly used after in situ preparation. On the other hand, cationic gold(I) complex (2a) prepared from AgNTf₂ salt is quite stable and the related crystals can be isolated. The complex 2a is soluble in most commonly used solvents and shows high reactivity. In addition, 2a catalyzed cycloisomerizations of enynes proceed successfully even when small amounts of catalyst (0.1 mol%) are used. Now, cationic gold(I) catalysts-promoted novel organosynthetic reactions have been studied and developed. Thus, 1 is a convenient precatalyst available for the preparation of various cationic gold(I) complexes.