1,1’,1”-(2’,4’-dinitro-[1,1’-biphenyl]-2,4, 6-triyl)tripiperidine

: The compound 1,1’,1”-(2’,4’-dinitro-[1,1’-biphenyl]-2,4,6-triyl)tripiperidine was synthesized by S E Ar / S N Ar reaction between 1-ﬂuoro-2,4-dinitrobenzene and 1,3,5-tris( N -piperidinyl)benzene. The structure of the newly synthesized compound was elucidated based on 1 H-NMR, 13 C-NMR, ESI-MS, UV-Vis and IR spectroscopy.


Introduction
Aromatic substitution reaction (both S N Ar [1,2] and S E Ar [3,4]) is one of the most important reactions in organic chemistry.In particular, the combination between aromatic electrophiles and nucleophiles at the neutral carbon atom allows one to obtain highly conjugated architectures bearing both electron donor and acceptor moieties.This kind of compound is receiving growing attention in material chemistry fields, such as solar energy conversion [5] and optoelectronic devices [6].

Results
The synthesis of 1,1',1"-(2',4'-dinitro-[1,1'-biphenyl]-2,4,6-triyl)tripiperidine (4) (Scheme 1) was performed by S E Ar/S N Ar reaction between 1-fluoro-2,4-dinitrobenzene (1) and 1,3,5-tripiperidinylbenzene (2) in acetonitrile at room temperature.The addition of triethylamine was made to prevent the protonation of reagent 2 by hydrofluoric acid, which is formed during the reaction course and would lead to a decrease in yield.The reaction course follows the classic SNAr mechanism; however, in reactions involving halonitrobenzenes, the ability of the latter to add nucleophiles is due to the activating effect of the nitro group, thus, nucleophiles should be able to add to these arenes also at positions occupied by hydrogen, subsequently resulting also in the formation of σ H adducts [13].This process is faster than the competing process of addition to the carbon atom bearing a nucleofugal group, resulting in the "classic" SNAr reaction.Moreover, only when the σ H adduct cannot be transformed into the SNAr H reaction product is the SNAr reaction observed [14], as in the current case.
It must be noted that Effenberger [15] reported that the reaction between 2 and 1-chloro-2,4dinitrobenzene in 1:1 chloroform/ethanol at reflux did not occur.In the current case, the use of the more electrophilic fluoroderivative allowed us to obtain the novel compound, bearing contemporarily an electron donor and an electron acceptor moiety, which makes it of interest in the applied field as well as a potentially useful precursor in hair-dyeing technique.
Dark red solid, cubic crystals (recrystallized from CH3CN) m.At the end of the reaction, the product was purified by column chromatography on silica gel using a n-hexane/ethyl acetate ratio of 9/1 as eluent (yield 60%).The structure of the newly synthesized compound was elucidated based on 1 H-NMR, 13 C-NMR, ESI-MS, IR, and UV/Vis spectroscopy (see spectra in Supplementary Materials).
The reaction course follows the classic S N Ar mechanism; however, in reactions involving halonitrobenzenes, the ability of the latter to add nucleophiles is due to the activating effect of the nitro group, thus, nucleophiles should be able to add to these arenes also at positions occupied by hydrogen, subsequently resulting also in the formation of σ H adducts [13].This process is faster than the competing process of addition to the carbon atom bearing a nucleofugal group, resulting in the "classic" S N Ar reaction.Moreover, only when the σ H adduct cannot be transformed into the S N Ar H reaction product is the S N Ar reaction observed [14], as in the current case.
It must be noted that Effenberger [15] reported that the reaction between 2 and 1-chloro-2, 4-dinitrobenzene in 1:1 chloroform/ethanol at reflux did not occur.In the current case, the use of the more electrophilic fluoroderivative allowed us to obtain the novel compound, bearing contemporarily an electron donor and an electron acceptor moiety, which makes it of interest in the applied field as well as a potentially useful precursor in hair-dyeing technique.

Materials and Methods
The 1 H and 13 C spectra were recorded on a Mercury 400 (Varian, Palo Alto, CA, USA) spectrometer operating at 400 MHz (for 1 H-NMR) and at 100 MHz (for 13 C-NMR).Chemical shifts refer to the solvent for 1 H and 13 C-NMR (δ = 7.26 ppm and δ = 77.0ppm, respectively, for CDCl 3 ).Signal multiplicities were established by Distortionless Enhanced by Polarization Transfer (DEPT) experiments.Chemical shifts were measured in δ (ppm).J values are given in Hertz.Electron spray ionization mass spectra (ESI-MS) were recorded with a WATERS ZQ 4000 instrument (Waters Corporation, Milford, MA, USA).IR spectrum were recorded with a Fourier transform spectrophotometer PerkinElmer FT-IR Spectrum Two (Perkin Elmer, Waltham, MA, USA) in the 4000−800 cm −1 wavelength range using a NaCl cell.UV/Vis spectrum was recorded using a Perkin Elmer Lamba 12 spectrophotometer.Chromatographic purifications (FC) were carried out on glass columns packed with Merck (Merck & Co. Readington, NJ, USA) silica gel (Merck grade 9385, 230−400 Mesh particle size, 60 Å pore size) at medium pressure.Thin layer chromatography (TLC) was performed on silica gel60 F 254 coated aluminum foils (Fluka, Buchs, Switzerland).