Recent progress in the oxidative bromination of arenes and heteroarenes.

Oxidative bromination has been serving as a powerful tool for the synthesis of bromo-containing molecules, as this bromination strategy features environmental friendliness, high flexibility in reaction system design and wide abundance of bromide sources and oxidants. The past decade has witnessed a large number of efficient oxidative bromination reaction systems and novel brominated aromatics. This review summarizes recent developments in the field of oxidative preparation of bromoarenes and bromoheteroarenes covering from 2012 to 2022.

New Three-Component Bicyclization Leading to Densely Functionalized Pyrazolo[3,4-d]thiazolo[3,2-a]pyrimidines.

A novel three-component bicyclization for the efficient synthesis of densely functionalized pyrazolo[3,4-d]thiazolo[3,2-a]pyrimidines has been established from readily accessible aryl aldehydes, α-thiocyanate ketones and pyrazol-5-amines. The reaction pathway involves nucleophilic addition/5-exo-trig /6-endo-trig bicyclization sequence, resulting in continuous multiple bond-forming events including C-N and C-C bonds to rapidly a molecular complexity.

Microwave-assisted multicomponent reaction in water leading to highly regioselective formation of benzo[f]azulen-1-ones.

Microwave-assisted three-component reaction has been established for the regioselective synthesis of benzo[f]azulen-1-ones. The reaction was performed in aqueous media under microwave irradiation by using readily available and inexpensive starting materials. A total of 38 examples were examined to show a broad substrate scope and good overall yields (70-89%). The present new synthesis shows attractive green chemistry characteristics, such as the use of water as reaction media, concise one-pot conditions, short reaction periods (7-24 min), easy work-up/purification and reduced waste production without the use of any strong acids or metal promoters.

Multicomponent synthesis of poly-substituted benzo[a]pyrano[2,3-c]phenazine derivatives under microwave heating.

A new one-pot two-step tandem synthesis of highly functionalized benzo[a]pyrano[2,3-c]phenazine derivatives via microwave-assisted multicomponent reactions of 2-hydroxynaphthalene-1,4-dione, diamines, aldehydes, and malononitrile is reported. The procedures are facile, avoiding time-consuming and costly syntheses, tedious workup, and purifications of precursors, as well as protection/deprotection of functional groups. The method is expected to find application in the combinatorial synthesis of biologically active compounds, since phenazine and chromene motifs have a broad spectrum of biological activities.