Unusual Retention of Isoxazole Ring under the Influence of 3-(Substituted nitrophenyl)-2-Isoxazoline during Catalytic Hydrogenation of Isoxazoline-Substituted Isoxazole Systems

摘要

The cleavage of the isoxazole ring during the Raney-Ni-promoted catalytic hydrogenation is prevented under the influence of 3-(substituted nitrophenyl)-2-isoxazoline in isoxazoline-substituted isoxazole systems, produced via 1,3-dipolar cycloaddition either on the Baylis-Hillman derivatives or Grignard products. Unexpectedly, the hydrogenations in these diastereomeric compounds were observed to exclusively yield products, wherein the methoxycarbonyl and the hydroxyl or the acetyl groups exist syn to each other.