The catalyst-directed divergent synthesis,
commonly termed as “divergent
catalysis”, has emerged as a promising technique as it allows
chartering of structurally distinct products from common substrates
simply by modulating the catalyst system. In this regard, gold complexes
emerged as powerful catalysts as they offer unique reactivity profiles
as compared to various other transition metal catalysts, primarily
due to their salient electronic and geometrical features. Owing to
the tunable soft π-acidic nature, gold catalysts not only evolved
as superior contenders for catalyzing the reactions of alkynes, alkenes,
and allenes but also, more intriguingly, have been found to provide
divergent reaction pathways over other π-acid catalysts such
as Ag, Pt, Pd, Rh, Cu, In, Sc, Hg, Zn, etc. The recent past has witnessed
a renaissance in such examples wherein, by choosing gold catalysts
over other transition metal catalysts or by fine-tuning the ligands,
counteranions or oxidation states of the gold catalyst itself, a complete
reactivity switch was observed. However, reviews documenting such
examples are sporadic; as a result, most of the reports of this kind
remained scattered in the literature, thereby hampering further development
of this burgeoning field. By conceptualizing the idea of “Divergent
Gold Catalysis (DGC)”, this review aims to consolidate all
such reports and provide a unified approach necessary to pave the
way for further advancement of this exciting area. Based on the factors
governing the divergence in product formation, an explicit classification
of DGC has been provided. To gain a fundamental understanding of the
divergence in observed reactivities and selectivities, the review
is accompanied by mechanistic insights at appropriate places.
