THERMAL AND ACID-CATALYZED REARRANGEMENTS OF 5,6-DIHYDRO-4H-1,2-OXAZINES

被引:38
作者
FARAGHER, R [1 ]
GILCHRIST, TL [1 ]
机构
[1] UNIV LIVERPOOL,ROBERT ROBINSON LABS,LIVERPOOL L69 3BX,LANCASHIRE,ENGLAND
来源
JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 1 | 1979年 / 01期
关键词
D O I
10.1039/p19790000258
中图分类号
O62 [有机化学];
学科分类号
070303 ; 081704 ;
摘要
2-Arylpyridines have been isolated in good yields from the pyrolysis of 3-arylcyclopent[e]oxazines (1) in the melt above 200 °C; a mechanism is proposed for this reaction which involves tautomerism of the 4H- to 2H-oxazines, followed by cleavage of the N-O bond. A similar ring-opening occurs with the benzo-derivative (3). The oxazines are methylated at nitrogen by methyl fluorosulphonate and methylation facilitates the ring-opening. Acid-catalysed rearrangement of the cyclopent[e]oxazine (1a) takes a different course, giving the spiro-isomer (9) by cleavage of the C-O bond. Similarly, the furo-oxazine (2) is cleaved in acid to give α-(2-furyl)acetophenone oxime, which is further transformed into cis-3-(3-phenylisoxazol-5-yl)prop-2-enol (10a) in trifluoroacetic acid. Acid-catalysed ring-opening of 6-morpholino-3,6-diphenyl- 5,6-dihydro-4H-1,2-oxazine (16) results in the formation of the syn and anti mono-oximes of 1,4-diphenylbutane-1,4-dione.
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页码:258 / 262
页数:5
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