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.