二溴亞鐵輔佐4－炔醯胺環己－2－烯－1－酮分子內麥可加成反應：稠環γ－內醯胺化合物的合成

Abstract

本文探討路易士酸輔佐4－炔醯胺環己－2－烯－1－酮分子內環化反應，合成含氮γ－內醯胺化合物。使用4－炔醯胺環己－2－烯－1－酮為起始物，以四氫呋喃為溶劑在氮氣下，溴化亞鐵先活化炔醯胺而得到keteniminium中間體A，而溴陰離子加成至keteniminium 中α位置的碳上而得到中間體B，再進行分子內麥可加成環化反應，得到含三個連續立體中心的稠環γ－內醯胺化合物。此反應的優點是操作簡單、產率高、得到唯一的立體異構物、好的官能基容忍度與溫和的條件且不需添加額外的氧化劑就可以合成稠環γ－內醯胺化合物。

關鍵字：溴化亞鐵、炔醯胺、分子內麥可加成、稠環γ－內醯胺。

A novel synthesis of fused bicyclic γ-lactams is developed. Treatment of iron(II) bromide with 4-ynamido-tethered cyclohex-2-en-1-ones in THF under nitrogen proceeded via Michael-Addition to afford fused bicyclic γ-lactams in good yields. Activation of the ynamide with FeBr2 gives a keteniminium intermediate A. Addition of a bromide at the α-position of the keteniminium ion affords intermediate B which undergoes intramolecular Michael-Addition to give the fused bicyclic γ-lactams with three contiguous stereocenters after hydrolysis. The reactions are procedurally simple, excellently diastereoselective and high yielding, producing fused bicyclic γ-lactams under mild conditions without an additional oxidizing reagent.

Keywords: iron(II) bromide, ynamide, Michael-Addition, fused bicyclic γ-lactams.