The
merging of click chemistry with discrete photochemical processes
has led to the creation of a new class of click reactions, collectively
known as photoclick chemistry. These light-triggered click reactions
allow the synthesis of diverse organic structures in a rapid and precise
manner under mild conditions. Because light offers unparalleled spatiotemporal
control over the generation of the reactive intermediates, photoclick
chemistry has become an indispensable tool for a wide range of spatially
addressable applications including surface functionalization, polymer
conjugation and cross-linking, and biomolecular labeling in the native
cellular environment. Over the past decade, a growing number of photoclick
reactions have been developed, especially those based on the 1,3-dipolar
cycloadditions and Diels–Alder reactions owing to their excellent
reaction kinetics, selectivity, and biocompatibility. This review
summarizes the recent advances in the development of photoclick reactions
and their applications in chemical biology and materials science.
A particular emphasis is placed on the historical contexts and mechanistic
insights into each of the selected reactions. The in-depth discussion
presented here should stimulate further development of the field,
including the design of new photoactivation modalities, the continuous
expansion of λ-orthogonal tandem photoclick chemistry, and the
innovative use of these unique tools in bioconjugation and nanomaterial
synthesis.
Site selectivity is an inherent challenge in C–H functionalization reactions. The most intensively sought‐after approaches have involved the employment of Lewis‐basic coordinating groups to direct a metal to a proximal site, in the process generating a metallacycle capable of further organometallic reactivity. In the recent years considerable effort has been directed towards the development of new transformations involving transition‐metal‐mediated C–H functionalization directed by weakly coordinating groups. This microreview focuses on the role and utility of amides and anilides in directed, proximal C–H bond functionalization reactions.
A new ruthenium-catalyzed, heteroatom-directed
strategy for C–H
allylation of indoles is described. The use of allyl alcohols as coupling
partners as well as pyridine as the removable directing group is highlighted.
This methodology provides access to C2-allylated indoles by utilizing
a strategy that does not require prefunctionalization of either of
the coupling partners.
Here we report the design of a superfast
bioorthogonal ligation
reactant pair comprising a sterically shielded, sulfonated tetrazole
and bicyclo[6.1.0]non-4-yn-9-ylmethanol (BCN). The design involves
placing a pair of water-soluble N-sulfonylpyrrole
substituents at the C-phenyl ring of diphenyltetrazoles to favor the
photoinduced cycloaddition reaction over the competing nucleophilic
additions. First-principles computations provide vital insights into
the origin of the tetrazole–BCN cycloaddition’s superior
kinetics compared to the tetrazole–spirohexene cycloaddition.
The tetrazole–BCN cycloaddition also enabled rapid bioorthogonal
labeling of glucagon receptors on live cells in as little as 15 s.
A unique, ruthenium-catalyzed, [3 + 3] annulation of anilines with allyl alcohols in the synthesis of substituted quinolines is reported. The method employs a traceless directing group strategy in the proximal C-H bond activation and represents a one-pot Domino synthesis of quinolines from anilines.
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