3,3,3-Tribromo-1-nitropropene: Synthesis and structure

Reactions of 3,3,3-Trihalogeno-1-nitropropenes with Arenes in the Superacid CF3SO3H: Synthesis of (Z)-3,3,3-Trihalogeno-1,2-diarylpropan-1-one Oximes and Study on the Reaction Mechanism

“…Reactions of CHal 3nitroethylenes 1a−c with para-xylene resulted in the formation of oximes 2c, 3b, 4b, respectively. A double set of signals with different integral ratios was observed in 1 H, 13 C, 19 F (for 2c) NMR spectra of these compounds in CDCl 3 at room temperature (see the Experimental Section and the Supporting Information). In this regard, it was suggested that, for these and other oximes, an atropoisomeric equilibrium may exist in solution due to the restricted rotation of the bulky CHal 3 group and aryl substituents.…”

“…To check this hypothesis, 1 H, 19 F (for 2c) NMR spectra of 2c, 3b, 4b were recorded in DMSO-D 6 at different temperatures from 25 to 120 °C. Upon increasing temperature, a broadening of NMR signals was observed, followed by their coalescence and again narrowing (Figure 2; see other spectra in the Supporting Information).…”

“…The samples were prepared by dissolving of CHal 3nitroethylenes 1a−c in TfOH directly in NMR tubes at room temperature. 1 H, 13 C, 19 F NMR data of initial compounds 1a−c (in CDCl 3 ) and the corresponding cations Aa−c (in TfOH) are presented in Table 6 (see spectra in the Supporting Information). A signal of the proton bonded to the nitro group was not detected in 1 H NMR spectra due to the fast proton exchange in superacidic medium.…”

“…These species afforded only undetectable water-soluble compounds. A careful examination of NMR spectra of these unknown cations showed that they have two new signals in 19 F NMR spectra in the range of δ −73.8 to −74.5 ppm, which may correspond to the triflate group coming from TfOH (see spectra in the Supporting Information). In 1 H NMR spectra, signals at δ ∼ 12.2 ppm most probably belong to the proton bonded to nitrogen of the oxime group (see below spectrum of N-protonated form of oxime E1 in Figure 4).…”

“…The NMR spectra of solutions of compounds in CDCl 3 or DMSO-d 6 were recorded at 400, 376, and 100 MHz for 1 H, 19 F and 13 C NMR spectra, respectively, at 25 °C. The solvent residual signals of CDCl 3 (δ 7.26 ppm) or DMSO-d 6 (δ 2.50 ppm) for 1 H NMR spectra and the carbon signals of CDCl 3 (δ 77.0 ppm) or DMSO-D 6 (δ 39.52 ppm) for 13 C NMR spectra were used as references.…”