Thermal rearrangements of tetrahydroimidazo[1,5-b]isoxazole-2,3-dicarboxylates. Synthesis of 3H-imidazol-1-ium ylides and their silver derivatives
作者:Necdet Coşkun、Meliha Çetin
DOI:10.1016/j.tet.2010.01.037
日期:2010.3
Isoxazolines 2 from the cycloaddition of imidazoline 3-oxides 1 with DMAD undergo rearrangement to 3,4-dihydro-2H-imidazol-1-ium-1-(1,2-bis-methoxycarbonyl-2-oxo-ethanides) 3, which spontaneously undergo elimination to give 3H-imidazol-1-ium-1-(1,2-bis-methoxycarbonyl-2-oxo-ethanides) 5 or 1H-imidazoles 6 when heated in toluene at reflux. The presence of the aromatic ring at C-6 decelerated the conversion
异恶唑啉2从咪唑啉-3-氧化物环加成1与DMAD经历重排,以3,4-二氢-2- ħ咪唑-1-鎓-1-(1,2-双-甲氧基羰基-2-氧代ethanides)3,当在甲苯中加热回流时,其自发消除,得到3 H-咪唑-1-鎓-1-(1,2-双-甲氧基羰基-2-氧代乙烷)5或1 H-咪唑6。C-6上芳环的存在降低了转化率,并提高了5的收率。极性比甲苯强的溶剂(例如DMSO)可实现2到6的定量转化在温和条件下,而在极性较小的溶剂(如CCl 4)中,反应速率降低,5的收率提高。C-2未取代的内鎓盐5用银处理过的2 O或硝酸银3中的的Et存在下3 Ñ在室温下,得到C-2的金属化衍生物9在良好的产率。