Dioxopyrroline. L. Skeletal Rearrangements of 7-Vinyl-7-trimethylsilyloxy-5-ethoxycarbonyl-1-phenyl-2-azabicyclo(3.2.0)heptane-3,4-diones under Thermal, Basic, and Acidic Conditions.
作者:Takehiro SANO、Jun TODA、Yoshisuke TSUDA
DOI:10.1248/cpb.40.36
日期:——
The oxyvinylcyclobutanes (2), photoadducts of the dioxopyrrolines (1) to trimethylsilyloxybutadienes, undergo two different types of skeletal rearrangements depending on the reaction conditions. Thermolysis of 2 caused expansion of the cyclobutane ring by a 1, 3-shift of the C1-C7 bond toward the vinyl group, giving rise to the hydroindoles (3) in moderate yields. This 1, 3-shift was enormously accelerated when an alkoxide was generated by the action of tetrabutylammonium fluoride (TBAF) on trimethylsilyloxyvinylcyclobutanes. Thus, 2a-d, on treatment with TBAF at -30°C, provided hydroindole derivatives in good yields, though in some cases (2a, b) accompanied with by-products (10). This demonstrates that the [2+2] photoannulation of dioxopyrroline, when coupled with the anionic 1, 3-shift, provides an efficient synthetic route to functionalized hydroindoles. Under acidic conditions, the oxyvinylcyclobutanes(2) rearranged to give exclusively the 2-azatricyclo[4.3.0.04, 9]nonanes (10), whose formation was rationalized in terms of the intramolecular Prins-type cyclization with concomitant expansion of the cyclobutane ring by 1, 2-shift of the C1-C7 bond toward the vinyl group.
氧乙烯基环丁烷(2),二氧吡咯烷(1)与三甲基硅氧基丁二烯的加成物,根据反应条件的不同,会发生两种不同的骨架重排。热解2使得环丁烷环通过C1-C7键向乙烯基的1,3-迁移而扩张,中等产率地生成氢茚(3)。当通过四丁基氟化铵(TBAF)的作用在三甲基硅氧基乙烯基环丁烷中产生醇盐时,这种1,3-迁移极大加速。因此,2a-d在-30°C下与TBAF处理,以良好产率提供氢茚衍生物,尽管在某些情况下(2a, b)伴有副产物(10)。这表明,[2+2]光环加成反应与阴离子的1,3-迁移相结合,为功能化氢茚提供了有效的合成途径。在酸性条件下,氧乙烯基环丁烷(2)重排,唯一地生成2-氮杂三环[4.3.0.04,9]壬烷(10),其形成可以解释为通过C1-C7键向乙烯基的1,2-迁移伴随着环丁烷环的扩张,发生的分子内Prins型环化反应。