Regiochemistry in radical cyclizations (5-endo versus 4-exo) of N-(2-phenylthio- and 2-phenylcyclohex-1-enyl)-α-halo amides
作者:Hiroyuki Ishibashi、Kazuya Kodama、Masahiro Higuchi、Osamu Muraoka、Genzoh Tanabe、Yoshifumi Takeda
DOI:10.1016/s0040-4020(01)00747-5
日期:2001.9
Bu3SnH-mediated radical cyclization of N-(2-phenylthiocyclohex-1-enyl)-α-halo amides was examined. Bromoacetamide 9a having no substituent α to the halogen atom cyclized exclusively in a 4-exo-trig manner, whereas the fully substituted haloamides 9c and 9e gave 5-endo-trig cyclization products. The mono-substituted haloamides 9b and 9d showed an intermediate behavior to give a mixture of 4-exo and
研究了Bu 3 SnH介导的N-(2-苯基硫代环己-1-烯基)-α-卤代酰胺的自由基环化。在卤素原子上没有取代基的溴乙酰胺9a仅以4- exo - trig方式环化,而完全取代的卤代酰胺9c和9e得到5- endo - trig环化产物。单取代的卤代酰胺9b和9d表现出中间行为,可生成4- exo和5- endo的混合物环化产品。关于反应温度的影响的实验结果表明,在低温下,即在动力学控制的条件下,以4- exo - trig环化为主。在另一方面,2 phenylcyclohex-1烯基同系部22b和22C完全得到5-远藤环化产物。