= CO2Et, COMe, SO2Me, CONH2) at ambient temperature in the presence of base to give [3 + 2]-cycloadducts by stepwise [3 + 2]-cycloaddition of the intermediate pyridinium ylides. Treatment of the crude reaction mixtures with 1 equiv. of chloranil and atmospheric oxygen in the presence of sodium hydroxide gave 1-(ethoxycarbonyl)indolizines by dehydrogenation and elimination of the acceptor group (Acc)
吡啶盐 Py+-
CH2-EWG (EWG = CO2Et, CONEt2, CN, COMe,
COPh) 与迈克尔受体 Ar-CH=C(CO2Et)(Acc) (Acc = CO2Et, COMe, SO2Me, CONH2) 在室温下反应碱的存在通过中间体
吡啶鎓叶立德的逐步[3 + 2]-环加成得到[3 + 2]-环加合物。用1当量处理粗反应混合物。通过脱氢和消除受体基团 (Acc),在
氢氧化钠的存在下将
氯苯醌和大气中的
氧气转化为 1-(乙氧基羰基)
吲哚腙。从 Py+- CN 和 iPr-CH=C(CO2Et)2 也获得了良好的
吲哚嗪收率,这表明该方法不限于芳香迈克尔受体。结构相关的
异喹啉盐与迈克尔受体类似地反应生成
吡咯并[2,1-a]
异喹啉。