Iridium/Copper‐Catalyzed Oxidative C−H/O−H Annulation of Benzoic Acids with Saturated Ketones for Accessing 3‐Substituted Phthalides

Recent advances in carboxyl-directed dimerizations and cascade annulations via C-H activations

C-H functionalization provides an efficient route to construct complex organic molecules. The introduction of directing groups enhances the site-selectivity of the reaction. Carboxyl as a directing group can be easily transformed into other functional groups afterwards. Due to its good reactivity, it can undergo cascade annulation reactions to build valuable heterocycle skeletons in one pot. Moreover, carboxyl can easily be removed via decarboxylation, which allows it to serve as a unique traceless directing group in C-H functionalization. These characteristics make carboxyl a promising directing group, which is superior to nitrogen-containing compounds with strong coordination ability to a certain extent. This feature article reviews the applications of carboxyl as a classical directing group and a unique traceless-directing group in cascade annulation reactions to access diverse carbocycles and heterocycles.

Oxidative Tandem Cyclization of Aromatic Acids with (Benzo)thiophenes: One-Pot Access to Planar Sulfur-Containing Polycyclic Heteroarenes for Lipid-Droplet-Targeted Probes

The efficient construction of π-conjugated polycyclic heteroarenes represents a significant task in the field of functional materials. A one-step oxidative tandem cyclization of aromatic acids with (benzo)thiophenes was developed to access planar sulfur-containing polycyclic heteroarenes. This protocol undergoes intermolecular cross-dehydrogenative coupling followed by intramolecular Friedel-Crafts acylation and provides a facile pathway to planar polycyclic compounds from inexpensive reactants. The synthesized heteroarenes serving as lipid-droplet-targeted probes exhibit outstanding performance with favorable biocompatibility and photostability.

Photoredox-Catalyzed Acyl Lactonization of Alkenes with Aldehydes: Synthesis of Acyl Lactones

An acyl lactonization of alkenes with aldehydes under visible-light photoredox catalysis is described. With the protocol, a broad scope of alkenoic acids and aldehydes could be compatible and good functional group tolerance is obtained. A series of acyl lactones are obtained with isolated yields ranging from 50-95%. Mechanistic studies revealed that the transformation should proceed via a radical chain process.

Isoindolinone synthesis through Rh/Cu-catalyzed oxidative C-H/N-H annulation of N-methoxy benzamides with saturated ketones

The synthesis of isoindolinones from N-methoxy benzamides and saturated ketones via a bimetallic tandem catalytic annulation has been accomplished. The reaction is catalyzed by a Rh/Cu-cocatalytic system and proceeds via the combination of Cu-catalyzed dehydrogenation of ketones and Rh-catalyzed direct C-H functionalization with the assistance of the N-methoxy amide group which also acts as an oxidant to regenerate the Rh catalyst. This method shows good compatibility with a wide range of substrates and functional groups, and provides an alternative strategy to obtain diverse isoindolinones.