Synthetic Reactions of Isoxazoline 2-oxides. Part XIV. New Route to 1,3,3a,8a-Tetrahydro-2H-benzofuro(2,3-b)pyrrol-2-ones from Methyl .ALPHA.-Hydroxy-4H-1,2-benzoxazine-4-acetates Obtained by Ring Transformation of 4-Aryl-2-isoxazoline 2-Oxides.
作者:Kazuho HARADA、Eisuke KAJI、Kiyobumi TAKAHASHI、Shonosuke ZEN
DOI:10.1248/cpb.42.1562
日期:——
4-Aryl-2-isoxazoline 2-oxides (1) were converted to methyl α-hydroxy-3-methoxycarbonyl-4H-1, 2-benzoxazine-4-acetates (3) upon treatment with a Lewis acid such as titanium tetrachloride. The structure of 3 was confirmed by X-ray analysis. Tosylates of 3 were treated with triethylamine to yield (E)- and (Z)- isomers of olefins (5) with (E)-preference. Catalytic reduction of each isomer of 5 produced 5, 8a-disubstituted 1, 3, 3a, 8a-tetrahydro-2H-benzofuro[2, 3-b]pyrrol-2-ones (6) in moderate yields.
4 芳基-2-异噁唑啉 2-氧化物(1)经路易斯酸(如四氯化钛)处理后,转化为 α-羟基-3-甲氧羰基-4H-1, 2-苯并噁嗪-4-乙酸甲酯(3)。X 射线分析证实了 3 的结构。3 的对甲苯磺酸盐经三乙胺处理后,可生成(E)-和(Z)-烯烃异构体(5),其中(E)-优先。催化还原 5 的每种异构体,以中等产率生成 5,8a-二取代的 1,3,3a,8a-四氢-2H-苯并呋喃并[2,3-b]吡咯-2-酮(6)。