Ring Expansion Reaction of 4-Substituted 5-[(Methylsulfonyloxy)methy1]3-methoxycarbony1-2-Isoxazoline 2-O x i d e Methanesulfonates by Use of Titanium Tetrabromide

Abstract

trans-4-Substituted 5-[(methylsulfonyloxy)methy1]-3-methoxycarbony1-2-isoxazoline 2oxide (3 a-d) were prepared through mesylation of the corresponding 5-hydroxymethyl derivatives (2 a-d), which were prepared from trans-4-substituted 3, 5-his(methoxycarbony1)-2isoxazoline 2-oxides (1 a-d). Compounds (3 a-d) were then allowed to react with titanium tetrabromide to afford ring expansion products, cis-4-substituted 5-hydroxy-3-methoxycarbonyl5, 6-dihydro-4 H-1, 2-oxazines (4 a-d).