Iodine-Catalyzed Cyclization of o-Nitrothiophenols with Cyclohexanones to Phenothiazines
Yinglin Zhao1, Jin Zhang1, Jingwu Zhang2
1Engineering Research Centre of Pharmaceutical Process Chemistry, Ministry of Education; School of Pharmacy, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, P. R. China.
Abstract:
Here, a novel iodine-catalyzed direct cyclization of o-nitrothiophenols with cyclohexanones to phenothiazines has been described without external oxidants and hydrogen acceptors. The nitro of o-nitrothiophenol works as both a hydrogen acceptor and a coupling group, and water is the only byproduct. The reaction involves the reduction of nitro groups, C-H bond thioetherification, and C-H bond dehydroaromatization. This scheme offers broad synthetic value for further elaborations, as exemplified by a 3-step total synthesis of antipsychotic chlorpromazine.
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