Cycloaddition of 2H-Pyran-2-thiones with Nitroso Derivatives. An Unexpected Cycloaddition-Rearrangement Reaction
作者:Albert Defoin、G�rard Augelmann、Hans Fritz、Guillaume Geffroy、Christian Schmidlin、Jacques Streith
DOI:10.1002/hlca.19850680724
日期:1985.11.13
Reaction of pyran-2-thiones 4 with nitroso derivatives led surprisingly to type-8 (19) adducts which proved to be isomeric with the initially expected primary Diels-Alder cycloadducts 5. Methyl 2-thioxo-2H-pyran-5-carboxylate (4f), when reacted with nitrosobenzene at -10°, led quantitatively to the thieto-oxazine intermediate 13, which turned out to be the cornerstone of the complex cycloaddition-rearrangement
吡喃-2-硫酮的反应4与导致令人惊奇的亚硝基衍生物型- 8(19被证明是同分异构体与最初的预期主要)加合物狄尔斯-阿尔德cycloadducts 5。当在-10°下与亚硝基苯反应时,2-thioxo-2 H -pyran-5-羧酸甲酯(4f)定量地导致硫代恶嗪中间体13转化为复杂的环加成重排5 的基石。8个反应途径(方案3)。差示扫描量热法,与18a 19a相同转化,被允许证明该多步重排总体上是高温放热过程,最终产物19代表沿着该反应路径的能量吸收器。