Asian Journal of Organic Chemistry

Bottoms up! 3,7-Functionalized hexaphyrins were synthesized by a stepwise bottom-up route, in which dipyrromethane Sn⁴⁺ complexes served as prefunctionalized precursors. Both hexaphyrins have rectangular conformations and are stable during usual manipulations in air in spite of their meso-free structures.

Not so scand-alous: We report a scandium(III) triflate catalyzed intramolecular Friedel–Crafts alkylation for the synthesis of 3-hydroxy-2-oxindoles. In comparison with nucleophilic conjugate additions of organometallic or electron-rich reagents to isatins and intramolecular addition of aryl chlorides to ketoamides, this protocol is simple, produces less waste, and omits organometallic reagents and halogenations. Bn=benzyl; DME=1,2-dimethoxyethane.

TiCl-ing your fancy: A simple and highly efficient synthetic method for the preparation of indolizines from the reaction of 2-enoylpyridines with sulfonamides in the presence of TiCl₄ under mild conditions has been developed. A subsequent phosphine-catalyzed aza-Michael reaction of the corresponding indolizines with vinyl ketones and activated allenes was also developed, which affords highly functionalized indolizines in excellent yields under mild conditions.

PBI Friday: Functional perylene bisimide assemblies that are constructed based on complementary multiple hydrogen-bonding interactions are reviewed. Supramolecular engineering of well-defined, hydrogen-bonded oligomers or polymers results in the formation of predictable extended assemblies through π–π stacking interactions. The unique optoelectronic and stimuli-responsive properties as well as the various morphologies of such assemblies are also introduced.

Robust catalysts: Recently, nitrogen-based ligands have attracted attention with regard to their possible applications in palladium-catalyzed direct CH arylations because of the unique reactivity of the resulting catalytic systems. This Focus Review examines recent advances in direct CH arylation of heteroarenes through the use of palladium/nitrogen-based ligand systems.

Know what imine? Methods used for imine synthesis that involve metal catalysts, including Ru, Au, V, Cu, Mn, Co, and Pd, as well as photocatalysis, electrocatalysis, organocatalysis, and other techniques are discussed. Special attention is paid to the condensation of carbonyl compounds/alcohols with amines, direct oxidation of amines to give imines, and copper-catalyzed imine synthesis, as copper offers more sustainable approaches to catalysis.

Breathing space: A fast and efficient protocol for the synthesis of heterobiaryls by a Pd/C-catalyzed, ligand-free, aqueous Suzuki reaction has been developed. The results demonstrate that the Pd/C-catalyzed heterogeneous Suzuki reaction is promoted by oxygen.

Ready, amine, fire! Amine catalysis is a useful and well-studied method for constructing a wide variety of chiral scaffolds in asymmetric synthesis. However, organocatalysis with amines that is not centered on asymmetric transformations is also developing at a rapid rate. In this Focus Review, reports on amine catalyzed non-asymmetric transformations are examined.

Activate! Pyrroles, indoles, and carbazoles are among the most important families of nitrogen-containing heterocycles that occur frequently in functional molecules. This Focus Review describes recent advances in transition-metal-catalyzed CH activation approaches for making these privileged heterocycles. The reactions discussed here showcase the latest developments in organometallic chemistry and homogeneous catalysis.

A snapshot: The structure-reactivity relationship of three classes of widely used photolabile protecting groups (PPGs), the 2-nitrobenzyl series of PPGs, carbonyl-based PPGs, and benzyl-based PPGs, is summarized. Recent efforts in developing new salicyl-based carbonyl PPGs and trityl-based PPGs for direct release of alcohols from PPG-protected hydroxy groups are also discussed.