Reaction of ThiocarbonylS-Methylides with Acetylenic Dipolarophiles and an Unexpected Rearrangement of the Cycloadducts
作者:Tomasz Gendek、Grzegorz Mlostoń、Anthony Linden、Heinz Heimgartner
DOI:10.1002/1522-2675(200202)85:2<451::aid-hlca451>3.0.co;2-9
日期:2002.2
cycloaddition of 2,2,4,4-tetramethyl-3-thioxocyclobutanone S-methylide (2a), generated in situ by thermal extrusion of N2 from the corresponding 2,5-dihydro-1,3,4-thiadiazole 1a, with electron-deficient acetylenic compounds yields spirocyclic 2,5-dihydrothiophene derivatives of type 4 (Scheme 2). Mixtures of diastereoisomers are obtained in the case of propiolates. The strained cyclooctyne also undergoes smooth
2,2,4,4-tetramethyl-3-thioxocyclobutanone S-methylide (2a) 的 1,3-偶极环加成反应,通过 N2 从相应的 2,5-dihydro-1,3,4 热挤压原位生成-噻二唑 1a 与缺电子炔属化合物产生 4 型螺环 2,5-二氢噻吩衍生物(方案 2)。在丙炔酸盐的情况下获得非对映异构体的混合物。应变的环辛炔还与硫酮 S-甲基化物进行平滑的环加成反应(方案 3)。在酸性条件下,通过环丁酮环的开环和五元环的芳构化,4 型和 6a 型螺环产物异构化为 7 型噻吩衍生物(方案 4)。