Catalytic Cycloisomerization-Oxidative Cyclization Reaction Sequence of Enyne Diesters Derived from 2-Propargyloxyarylaldehydes

Enyne diesters derived from 2-propargyloxyarylaldehydes are converted into 2-oxopyranochromenes via In(OTf)3-catalyzed cycloisomerization and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ)-mediated oxidative cyclization reaction sequence in one pot. The process possesses broad substrate scope and good functional group compatibility and generates various 4-(hetero)aryl-substituted 2-oxopyranochromenes in 32-79% yields (over two steps). 2-Oxopyranochromenes undergo selective decarboxylation under Krapcho conditions. When treated with aliphatic secondary amines in DMF, 2-oxopyranochromenes undergo decarboxylative amination at ambient temperature to generate 2-amino-substituted functionalized chromenes in good yields.

PIDA-mediated Oxidative Decarboxylation of Oxamic Acids. The Role of Radical Acidity Enhancement

The PIDA-mediated oxidative decarboxylation of oxamic acids in the presence of alcohols is shown to afford the corresponding urethanes under thermal conditions. Computational and experimental mechanistic exploration allows to rationalize the different reactivity of PIDA as compared to related cyclic BI-OAc and highlights the importance of the enhanced acidity of the proton in the carbamoyl radical intermediate.

C(sp3)-H Ritter amination by excitation of in situ generated iodine(III)-BF3 complexes

Visible light excitation of iodine(III)-BF₃ complex enables the formation of carbocations from C(sp³)-H bonds. The complexes are generated catalytically from iodoarene, carboxylate ligand, the oxidizing agent Selectfluor, and the Lewis acid BF₃. This modular catalytic system allows the formation of synthetically valuable amine derivatives without a metal- or photocatalyst.