Synthesis of seven-membered ring diazepin-2-ones via palladium-catalyzed highly regioselective cyclization of 2-vinylpyrrolidines with aryl isocyanates

The first palladium-catalyzed ring-expansion reaction of 2-vinylpyrrolidines with aryl isocyanates to form seven-membered ring heterocycles is described. This regioselective reaction requires 5 mol % of Pd(2)(dba)(3).CHCl(3) and 10 mol % of dppp at 40-60 degrees C in THF and results in the formation of 1,3-diazepin-2-ones in good isolated yields. When Pd(OAc)(2) and PPh(3) were utilized in the reaction, an intramolecular hydrogen migration occurs resulting in the formation of conjugated diene derivatives of urea.