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Synthesis 1987; 1987(3): 242-245
DOI: 10.1055/s-1987-27901
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Facile Access to 6-Methoxy-1,2,3,6-tetrahydro- and 4-Hydroxy-1,2,3,4-tetrahydropyridines by Electrochemical Haloalkoxylation-Dehydrohalogenation Sequence as a Key Operation

Sigeru Torii* , Tsutomu Inokuchi, Fumihiko Akahosi, Minoru Kubota
  • *Department of Industrial Chemistry, School of Engineering, Okayama University, Okayama 700, Japan
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Publication Date:
12 September 2002 (online)

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A facile procedure for the synthesis of N-ethoxycarbonyl-6-methoxy-1,2,3,6-tetrahydropyridines 6 and N-ethoxycarbonyl-4-hydroxy-1,2,3,4-tetrahydropyridines 7 from piperidines 1 is described. The electrochemical halomethoxylation of N-ethoxycarbonyl-1,2,3,4-tetrahydropyridines 4 (easily accessible from 1 by ethoxycarbonylation followed by electrooxidative methoxylation and acid-catalyzed elimination of methanol) in a CH3OH-NR4X(X = Cl, Br, I)-(Pt)-(Pt) system provides N-ethoxycarbonyl-3-halo-2-methoxypiperidines 5 in 74-90 % yields. Dehydrohalogenation of iodides 5 (X = 1) with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in toluene gave the desired olefin 6, which was isomerized in aqueous acetic acid to afford the alcohol 7 in 34-55% yields (from 5). The procedure is also applicable to the synthesis of seven membered derivatives 6f and 7f from 1f.