RESUMEN
A convenient one-pot benzannulation of regioisomeric 2- or 3-substituted furan and thiophene ynones with a range of nitromethanes has been discovered to directly access densely and diversely functionalized benzofurans and benzothiophenes. In this protocol, the nitro group in nitromethanes functions as recursive carbanion activator to setup tandem Michael addition-6π-electrocyclization, and its eventual sacrificial elimination facilitates aromatization and overall benzannulation. This benzannulation was also explored with furan/thiophene based o-halo ynones wherein a Michael addition-SNAr process operates and nitromethanes leave their imprint to deliver nitro substituted benzo-furans and -thiophenes.
RESUMEN
An efficient one-pot synthesis of 4-(1H)-quinolones through an orthogonal engagement of diverse o-haloaryl ynones with ammonia in the presence of Cu(I), involving tandem Michael addition and ArCsp2-N coupling, is presented. The substrate scope of this convenient protocol, wherein ammonium carbonate acts as both an in situ ammonia source and a base toward diverse 2-substituted 4-(1H)-quinolones, has been mapped and its efficacy validated through concise total synthesis of bioactive natural products pseudanes (IV, VII, VIII, and XII), graveoline, graveolinine, and waltherione F.
