Synthesis of imidazolocoumarins by the amide-directed oxidative cyclisation of enol-Ugi derivatives

Abstract

Hypervalent iodine regioselective C–H amidation of enol-Ugi adducts is controlled by a removable amide group.

Stefano Marcaccini: a pioneer in isocyanide chemistry

“…Marcos et al have recently developed an oxidative C(sp 3 )–H intramolecular imination of hydroxycoumarin enol-Ugi adduct derivatives ( 442 ) which leads to imidazolocoumarins ( 447 ) [ 149 ]. Interestingly, the regioselectivity of the reaction is controlled by the amide group derived from the enol-Ugi isocyanide component, which directs the functionalisation of the adjacent C(sp 3 )–H and then is lost as an isocyanate (Scheme 89 ).…”

Stereoselective Synthesis of 12-Tetrazolyl Substituted (E)-5H-Quinazolino[3,2-a]quinazolines via Sequential Ugi-Azide/Staudinger/aza-Wittig/Addition/Ag(I)-Catalyzed Cyclization

“…The isocyanide based multicomponent reactions (I-MCRs), especially Ugi four-component reactions, have played a vital role in organic and medicinal chemistry due to their efficient construction of small-molecule libraries in a mild one-pot fashion. , The Ugi-azide reactions have also provided a powerful method for synthesis of 1,5-disubstituted tetrazoles, as the carboxylic acid component is changed to hydrazoic acid (produced in situ from NaN 3 or TMS-N 3 ). − In recent years, the sequence of Ugi reaction and other organic reactions has been successfully applied in the synthesis of many heterocyclic compounds. − For example, the tandem post-Ugi cyclization and Gold­(I)-catalyzed regioselective annulation were utilized in the preparation of densely functionalized pyrrolo­[1,2- a ]­pyrazine-3,6­(2 H ,4 H )-diones in good to excellent yields . Diverse benzazepinoindoles were assembled in a step-economical, chemo- and regioselective fashion by an Ugi/gold-catalyzed alkyne hydroarylation/Michael addition sequence .…”