Pd-catalyzed oxidative amination of 2-alkenylquinazolin-4(3H)-ones: synthesis of methylene and vinyl derivatives of pyrrolo(pyrido)[2,1-b]quinazolinones

Abstract

When treated with the catalytic system Pd(OAc)₂/PPh₃/Cs₂CO₃/benzoquinone in dioxane or Pd(PPh₃)₂Cl₂/t-BuONa/Cs₂CO₃/benzoquinone in toluene, 2-butenylquinazolin-4(3H)-ones undergo intramolecular aza-Wacker cyclization to give methylene-substituted pyrrolo(pyrido)[2,1-b]quinazolinones. The latter catalytic system is also efficient in the reaction of pentenyl(hexenyl)quinazolin-4(3H)-ones but, in these cases, the aminopalladation of C–H multiple bonds significantly competed with allylic C(sp³)–H bond activation which leads to hitherto unknown vinyl-substituted pyrrolo(pyrido)[2,1-b]quinazolinones.