Radical cyclisations of methylenecyclopropyl azetidinones—synthesis of novel tricyclic β-lactams
作者:David J Penfold、Kurt Pike、Anthony Genge、Mike Anson、John Kitteringham、Jeremy D Kilburn
DOI:10.1016/s0040-4039(00)01860-8
日期:2000.12
azetidinones gives methylenecyclopropyl azetidinones, which can be converted to various radical cyclisation precursors. Attempted 4-exo cyclisation of 3 led only to reduced product, while cyclisation of 5, using CuCl/bipy, gave a carbacephem, via a 5-exo cyclisation, but in low yield. Cyclisation of 6 and 7, however, gave novel tricyclic β-lactams, as the result of 7-endo cyclisation, in good yield, and a
将双(亚甲基环丙基)铜锂加到乙酰氧基氮杂环丁酮中得到亚甲基环丙基氮杂环丁酮,其可被转化成各种自由基环化前体。试图4-外的环化3而环化只会导致还原产物,5,使用的CuCl /联吡啶,得到一头孢烯,经由5-外型环化,但是在低的产率。然而,由于7-内环化的结果,对6和7的环化产生了新颖的三环β-内酰胺,并且通过自由基级联序列,溴化物23的环化导致了三环β-内酰胺24。