Novel Diastereoselective Synthesis of Bicyclic β-Lactams through Radical Cyclization and Their Reduction toward 2-(1-Alkoxy-2-hydroxyethyl)piperidines and 2-(1-Alkoxy-2-hydroxyethyl)azepanes
作者:Erika Leemans、Matthias D'hooghe、Yves Dejaegher、Karl W. Törnroos、Norbert De Kimpe
DOI:10.1021/jo702263p
日期:2008.2.1
1-Allyl- and 1-(3-phenylallyl)-substituted 4-(2-bromo-1,1-dimethylethyl)azetidin-2-ones were transformed into 3-substituted 7-alkoxy-5,5-dimethyl-1-azabicyclo[4.2.0]octane-8-ones through radical cyclization by means of n-tributyltin hydride and AIBN in toluene with excellent diastereocontrol (≥99%). The radical cyclization of 4-(2-bromo-1,1-dimethylethyl)-1-(2-methylallyl)azetidin-2-ones afforded 8-alkoxy-3
将1-烯丙基和1-(3-苯基烯丙基)取代的4-(2-溴-1,1-二甲基乙基)氮杂环丁烷-2-酮转化为3-取代的7-烷氧基-5,5-二甲基-1-氮杂三环[4.2.0]辛烷-8-通过氢化正丁基三丁基锡和AIBN在甲苯中进行自由基环化,具有出色的非对映异构控制性(≥99%)。4-(2-溴-1,1-二甲基乙基)-1-(2-甲基烯丙基)氮杂环丁烷-2-酮的自由基环化提供了8-烷氧基-3,6,6-三甲基-1-氮杂双环[5.2.0 ] nonan-9-非对映异构体过量(75-78%)。1-氮杂双环[4.2.0]辛烷-8-酮和1-氮杂双环[5.2.0]壬南-9-酮与氢化铝锂的还原开环生成了新型的2-(1-烷氧基-2-羟乙基)哌啶和-azepanes,它们是作为单一异构体分离出来的。