Synthesis of Seven-Membered Ring Diazepin-2-ones via Palladium-Catalyzed Highly Regioselective Cyclization of 2-Vinylpyrrolidines with Aryl Isocyanates
摘要:
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).CHCl3 and 10 mol % of dppp at 40-60 degreesC in THF and results in the formation of 1,3-diazepin-2-ones in good isolated yields. When Pd(OAc)(2) and PPh3 were utilized in the reaction, an intramolecular hydrogen migration occurs resulting in the formation of conjugated diene derivatives of urea.