Koenigs and N e~ mann,~ in describing the preparation of 4-iodo-and 4-bromopiperidines, state that these 4-halogenopiperidines split halogen acid, in alkaline solution, to give tetrahydropyridine. Apparently, this compound was not isolated nor characterized as no ...
[Irfan, Muhammed; Petricci, Elena; Glasnov, Toma N.; Taddei, Maurizio; Kappe, C. Oliver European Journal of Organic Chemistry, 2009 , # 9 p. 1327 - 1334]