Investigations on regio- and stereoselectivities in cycloadditions involving α- (3-pyridyl)-<i>N</i>-phenylnitrone: Development of an efficient route to novel nicotine analogs
作者:Gurpinder Singh、M. P. S. Ishar、Navdeep K. Girdhar、Lakhwinder Singh
DOI:10.1002/jhet.5570420603
日期:2005.9
syn-5-methy-3-pyridyl-1-phenyl-isoxazolidine-5-carboxylate (8) and ethyl anti-5-methy-3-pyridyl-1-phenyl-isoxazolidine-4-carboxylate (10), respectively, in high yields. Reaction with N-Phenylmaleimide affords novel isoxazolidino-pyrro-lidinediones bearing a 3-pyridyl moiety (11, 12). A mechanistic rationalization of the obtained results in terms of electronic, steric and secondary interactions is proffered.
迄今为止,α-(3-吡啶基)-N-苯基硝酮(1)与单取代的富电子和电子中性偶极亲热物的热反应是区域和立体选择性(外向选择性),受LUMO-偶极-的控制HOMO-双极性亲和性相互作用,并以高收率提供顺式-5-取代-3-(3-吡啶基)-异恶唑烷(5)。对于缺乏电子的偶极亲子,例如丙烯腈,观察到区域选择性和立体选择性的损失,并且由于与HOMO-偶极-LUMO-dipolarophile相互作用的干预,在与甲基乙烯基酮和丙烯酸甲酯的反应中,区域选择性被逆转,得到4-取代基t 3-3-(3-吡啶基)-异恶唑烷(7)作为主要产品。硝酮(的反应1与二取代dipolarophiles如)甲基丙烯酸甲酯和乙基CORONATE配料甲基顺-5-甲基-3-吡啶基-1-苯基-异恶唑烷-5-羧酸酯(8)和乙基反-5-甲基-3-分别高产率地合成吡啶基-1-苯基-异恶唑烷-4-羧酸盐(10)。与N-苯基马来酰亚胺反应,得