Synthesis and crystal structures of five fluorinated diphenidine derivatives.

Diphenidine (), a dissociative anaesthetic, was first reported in 2013. Since then, a number of derivatives 2-methoxphenidine () have been produced by clandestine laboratories and sold as . Fluorinated diphenidines, namely, [1-(2,6-di-fluoro-phen-yl)-2-phenyl-eth-yl]di-methyl-aza-nium chloride, CHFN·Cl, (), [1-(2,6-di-fluoro-phen-yl)-2-phenyl-eth-yl](eth-yl)aza-nium chloride di-chloro-methane hemisolvate, 2CHFN·2Cl·CHCl, (), -but-yl[1-(2,6-di-fluoro-phen-yl)-2-phenyl-eth-yl]aza-nium chloride, CHFN·Cl, (), 1-[1-(2,6-di-fluoro-phen-yl)-2-phenyl-eth-yl]pyrrolidin-1-ium chloride, CHFN·Cl, (), and 1-[1-(2,3,4,5,6-penta-fluoro-phen-yl)-2-phenyl-eth-yl]piperidin-1-ium chloride, CHFN·Cl, (), were synthesized and structurally characterized by H, C and F NMR spectroscopy, and single-crystal X-ray diffraction. All five structures exhibit hydrogen bonding between the quaternary amine hydrogen atoms and the chlorine. The N-H⋯Cl distances for () and () range from 2.21 to 2.31 Å, whereas (), () and () exhibit shorter N-H⋯Cl distances (2.07-2.20 Å). Compounds () and () include pyrrolidine and piperidine rings, respectively; the pyrrolidine ring adopts an envelope conformation whereas the piperidine ring adopts a chair conformation. The crystal packing in compounds ()-() is characterized by C-H⋯π inter-actions; no π-π inter-actions are observed.