Alkenes and their derivatives are featured widely in
a variety
of natural products, pharmaceuticals, and advanced materials. Significant
efforts have been made toward the development of new and practical
methods to access this important class of compounds by selectively
activating the alkenyl C(sp2)–H bonds in recent
years. In this comprehensive review, we describe the state-of-the-art
strategies for the direct functionalization of alkenyl sp2 C–H and C–F bonds until June 2022. Moreover, metal-free,
photoredox, and electrochemical strategies are also covered. For clarity,
this review has been divided into two parts; the first part focuses
on currently available alkenyl sp2 C–H functionalization
methods using different alkene derivatives as the starting materials,
and the second part describes the alkenyl sp2 C–F
bond functionalization using easily accessible gem-difluoroalkenes as the starting material. This review includes the
scope, limitations, mechanistic studies, stereoselective control (using
directing groups as well as metal-migration strategies), and their
applications to complex molecule synthesis where appropriate. Overall,
this comprehensive review aims to document the considerable advancements,
current status, and emerging work by critically summarizing the contributions
of researchers working in this fascinating area and is expected to
stimulate novel, innovative, and broadly applicable strategies for
alkenyl sp2 C–H and C–F bond functionalizations
in the coming years.