Selective syntheses of benzoxazoles and N-(2-hydroxyaryl)pyrrolidin-2-ones from the corresponding cyclopropyl amides with PPh3/CX4

Benzoxazoles 2 can be smoothly synthesized by treatment of starting materials of N-(2-hydroxyaryl) cyclopropyl amides 1 with PPh3/CCl4 in acetonitrile in good yields. When PPh3/CBr4/MS 4 Å was used in the reaction system, the corresponding ring-expanding products 3 were obtained in moderate to good yields in acetonitrile at 80 °C. Using DCE as a solvent in this reaction, the corresponding 2-(3-chloropropyl)benzoxazoles 5 were obtained as major products.

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