Tetrahedron Letters

Dihydropyrazino-quinazolinedione chemotypes are complex and structurally challenging structures of biological interest, being found in the marine alkaloids such as brevianamide M-N and fumiquinazolines A-C. Herein we report the synthesis of this tricyclic system in three synthetic operations by means of an Ugi multi-component reaction (MCR) followed by a tandem N-acyliminium ion cyclization-intramolecular nucleophilic addition reaction sequence. Additional structural diversification for further library enrichment was also accomplished via sequential N-alkylation and N-acylation/sulfonation...

A series of pyridyl-substituted 3-hydroxy-2-oxyindoles have been prepared and reacted with arenes in superacid promoted Friedel-Crafts reactions. The product aryl-substituted 2-oxyindoles are formed in generally good yields. With substituted arenes such as toluene, bromobenzene, or ethyl salicylate, the Friedel-Crafts reactions occur with excellent regioselectivity. A mechanism is proposed involving dicationic, superelectrophilic species leading to the electrophilic aromatic substitution chemistry.