Nitrite sulphides. Part 10. Intramolecular 1,3-dipolar cycloadditions

摘要: Intramolecular 1,3-dipolar cycloadditions involving acetylenic and olefinic esters of o-hydroxybenzonitrile sulphide have been examined. The nitrite sulphides were generated by thermal decarboxylation the corresponding 1,3,4-oxathiazol-2-one. o-Phenylpropiolyloxy -amido derivatives (1a) (2a) afforded chromeno[4,3-c]isothiazolone (7a)(70%) isothiazolo[4,3-c]quinolinone (9a)(81%) respectively. Four products formed on thermolysis cinnamate (10); o-cyanophenyl cinnamates resulting from desulphuration sulphide; chromenoisothiazolones (7) cycloaddition followed dehydrogenation 4,5-dihydroisothiazole; chromeno[4,3-b]quinolinones (14); 4-amino-3-benzylchromenones (15). last two compounds are believed to be a pathway 2,5-dihydroisothiazole tautomer (17), extrusion ofsulphur, cyclisation or hydrogenation (Scheme 2). α- β-Methylcinnamate (19) (20) afforded, in addition by-products, dihydroisothiazole (21) 4-amino-3(α-styryl)chromenone (23)