2-Acetamido-3-thiophenecarboxylic acid ethyl esters 1 have been heated in HMPT to reflux temperature to produce 4,6-bis(dimethylamino)thieno[2,3-b]pyridines 7. Substituents in the 4 position of the thiophene ring were found to exert steric hindrance on the reaction. Only a multistep mechanism can account for the product 7. The intermediates 2–5 were also isolated in the reaction of 1a with HMPT.
将2-乙酰
氨基-3-
噻吩羧酸乙酯1在HM
PT中加热至回流温度,以产生4,6-双(二甲基
氨基)
噻吩并[2,3-b]吡啶7。发现
噻吩环的4位上的取代基对反应产生位阻。只有多步机制才能说明产品7。在1a与HM
PT的反应中也分离出了中间体2–5。