An efficient and scalable synthesis of substituted phenanthrenequinones by intramolecular Friedel-Crafts reaction of imidazolides |
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Authors: | Yoshikawa Naoki Doyle Austin Tan Lushi Murry Jerry A Akao Atsushi Kawasaki Masashi Sato Kimihiko |
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Institution: | Department of Process Research, Merck Research Laboratories, Merck & Co., Inc., Rahway, New Jersey 07065, USA. naoki_yoshikawa@merck.com |
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Abstract: | An efficient synthesis of 9,10-phenanthrenequinones is described. The two carbonyl groups were introduced by an orthoselective intermolecular Friedel-Crafts reaction of 3-methoxyphenol with ethyl chlorooxoacetate. The formation of a biaryl bond by Suzuki-Miyaura coupling reaction, followed by the hydrolysis of the ester, gave a biaryloxoacetic acid. Treatment of this acid with CDI gave the corresponding imidazolide. The ring closure to the desired phenanthrenequinone was accomplished by intramolecular Friedel-Crafts reaction of the imidazolide promoted by TiCl(4). |
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