In this review, we categorize C–O bond functionalization reactions according to their
underlying mechanisms, encompassing both C(sp²)–O and C(sp³)–O bond activations. While
nickel-based catalysts have dominated the early and continuing developments in this
area, recent efforts have expanded the scope to include a broader range of transition
metals. Although molecular transformations catalyzed by these alternative metals are
still in their infancy, they have yielded valuable mechanistic insights that are essential
for future advancements. Moreover, it has become increasingly clear that traditional
mechanistic frameworks are insufficient to fully explain the activation of inherently
unreactive C–O bonds. This has led to a surge of interest in alternative activation
paradigms, particularly dual activation strategies that exploit the synergistic roles
of multiple catalytic components. By systematically summarizing current strategies
for C–O bond activation, this review seeks to accelerate progress in the field and
offer conceptual guidance for the broader activation of otherwise inert bonds.
Keywords
C(sp
2)–O bond activation - C(sp
3)–O bond activation - Transition metal - Catalysis - Reaction mechanism - Dual activation
