Preparation of β-and γ-lactams via ring closures of unsaturated carbamoyl radicals derived from 1-carbamoyl-1-methylcyclohexa-2,5-dienes
作者:A. Franco Bella、Leon V. Jackson、John C. Walton
DOI:10.1039/b313932h
日期:——
1-Carbamoyl-1-methylcyclohexa-2,5-dienes produced the corresponding delocalised 1-carbamoyl-1-methylcyclohexa-2,5-dienyl radicals on treatment with radical initiators. At temperatures above ca. 300 K dissociation to produce toluene and aminoacyl (carbamoyl) radicals took place. The alternative dissociation of the 1-carbamoyl-1-methylcyclohexa-2,5-dienyl radicals to release methyl radicals and an aromatic amide did not compete. Aminoacyl radicals with allyl, butenyl or similar side chains underwent cyclisations. Moderate yields of N-benzyl-azetidin-2-ones and N-benzyl-pyrrolidin-2-ones were isolated for a range of substituents. The main by-products were N-benzyl-N-alkenylformamides. Ring closure did not take place to a significant extent for precursors with alk-2-ynyl or 2-cyanoalkyl side chains. An improved yield of 1,3-dibenzylazetidin-2-one was obtained by use of lauroyl peroxide as initiator and by inclusion of methyl thioglycolate as polarity reversal catalyst.
1- 氨基甲酰基-1-甲基环己-2,5-二烯在使用自由基引发剂处理时会产生相应的脱位 1- 氨基甲酰基-1-甲基环己-2,5-二烯自由基。在温度高于约在 300 K 以上的温度下会发生解离,生成甲苯和氨基酰(氨基甲酰基)自由基。1- 氨基甲酰基-1-甲基环己-2,5-二烯自由基解离生成甲基自由基和芳香族酰胺的过程并不竞争。带有烯丙基、丁烯基或类似侧链的氨基酰基发生了环化反应。在一系列取代基上分离出了中等产量的 N-苄基氮杂环丁烷-2-酮和 N-苄基吡咯烷-2-酮。主要副产物为 N-苄基-N-烯基甲酰胺。带有烷基-2-炔基或 2-氰基烷基侧链的前体没有明显的闭环现象。使用月桂酰过氧化物作为引发剂,并加入巯基乙酸甲酯作为极性反转催化剂,可提高 1,3-二苄基氮杂环丁烷-2-酮的产率。