Abstract
We first developed the synthesis of di- and trisubstituted isoxazole through transition metal-catalyzed cyclization of alkynyl oxime ethers. When O-allyl alkynyl oxime ether was treated with AuCl3, gold-catalyzed cyclization and [3,3]-sigmatropic rearrangement reaction proceeded to afford 3,4,5-trisubstituted isoxazole. In addition, treatment of O-benzyl alkynyl oxime ether with AgBF4 and phenol in THF gave 3,5-disubstituted isoxazole in high yield via cyclization and protonation.A regioselective intramolecular cyclization/halogenation reaction of N-alkoxy-o-alkynylbenzamides with CuCl2/NCS was also developed. The corresponding 3-(chloromethylene)isobenzofuran-1-ones were exclusively obtained via 5-exo-dig cyclization in moderate to excellent yields.
