Heating of the silylene protected dihydroxystyrene generated from the O-hydroxyacetophenone (3a) at 130-150°C for 15-48h in a sealed tube gave intramolecular [4+2]cycloaddition products (5 and 6). The addition of chloranil to the reaction mixture brought about an oxidative intramolecular [4+2]cycloaddition to give the linearly condensed peri-hydroxy aromatic compound(7a) in excellent yield. The generality of this cycloaddition and application to a short and efficient synthesis of the ABCD ring system of fredericamycin A are described.
将从O-羟基乙酰基苯(3a)生成的
硅烯保护二羟基
苯乙烯加热至130-150°C,在密闭管中反应15-48小时,得到了分子内[4+2]环加成产物(5和6)。向反应混合物中添加
氯萘导致了氧化性的分子内[4+2]环加成,良好产率地生成了线性缩合的peri-羟基芳香化合物(7a)。描述了这种环加成的普遍性及其在短而高效的弗雷德里卡霉素A AB
CD环体系合成中的应用。