Wittig homologation of 2-(chloromethyl)-2H-chromen-2-ol derivatives: a new facile synthesis of substituted 2,3-dihydrobenzoxepine-4-carboxylates |
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Authors: | Bhimapaka China Raju Gannerla Saidachary Jaladi Ashok Kumar |
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Institution: | Natural Products Chemistry Division, CSIR-Indian Institute of Chemical Technology, Hyderabad 500 607, India |
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Abstract: | Wittig homologation of 2-(chloromethyl)-2H-chromen-2-ol derivatives 2a–t with (ethoxycarbonylmethylene)triphenylphosphorane provided the 2-oxoethylidene-2,3-dihydrobenzoxepine-4-carboxy-lates 3a–t with Z (cis) selectivity. Various basic catalysts were studied for the reaction of 2-(chloromethyl)-2H-chromen-2-ol 2a with the combination of Wittig reagent to provide compound 3b. The reaction of 2-(chloromethyl)-2H-chromen-2-ol 2a with other Wittig reagents, such as methylene(triphenylene)phosphorane and (1-ethoxycarbonylethylidene)triphenylphosphorane provided ketone derivative 4a rather 2-oxoethylidene derivative 3b. The ketone derivative 4a was reacted with Wittig reagent (ethoxycarbonylmethylene)triphenylphosphorane to give 2,3-dihydrobenzoxepine-4-carboxylate 3b. The present approach is novel, straight forward and being reported for the first time. |
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