N. M. Karimova

1-ALKYL-2-TRIFLUOROMETHYLAZIRIDINES : THE BACISITY AND RING-OPENING REACTIONS UNDER THE ACTION OF ACIDS

The basicity of 1-alkyl-2-trifluoromethylaziridines is-two orders of magnitude lower than that of non-fluorinated analogs. Aziridines are stable to H2S and AcOH, but react with AcSH, HCl, HBr, H2SO4, TsOH, and picric acid to give products of ring-opening.

Addition of thiols to ethyl 4,4,4-trifluorocrotonate

Ethyl 4,4,4-trifluorocrotonate 1 readily adds aliphatic and aromatic thiols and aminothiols at the double bond in the presence of catalytic amounts of alkylamines and ammonia to give 3-thiolation products. Thiolacetic acid reacts with ester 1 in the absence of a catalyst at 100 °C.

Synthesis of 1,2,3,4-tetrachlorohexafluorobutane

The condensation of 1-iodo-1,2,2-trifluoro-1,2-dichloroethane induced by granulated Zn in the presence of catalytic amounts of AcOEt without a solvent results in 1,2,3,4-tetrachlorohexafluorobutane in high yield.

Nucleophilic substitution of bromine in vicinal bromotrifluoroalkylamines

SecondaryN-(2-bromo-3,3,3-trifluoropropyl)-N-alkylamines cyclize under the action of bases to yield aziridines. TertiaryN-(2-bromo-3,3,3-trifluoropropyl)amines react with S-nucleophiles to give products of bromine substitution.

Synthesis of some heterocycles containing CF3-group

Abstract Trifluoromethylated bromoalkylamines (I) are prepared via the addition of NH 3 and amines to trifluorobromopropene at mild conditions (20°C). Bromines atoms in I may undergo to inter- and intra-molecular nucleophilic substitution in spite of the strong passivating influence of the neighboring CF 3 -group. Interaction of tertiary amines (I) with the sulfur nucleophiles (100−150°C, 3h, in aprotic solvents) leads to CF 3 -derivatives of thioethanol amine (II). The intramolecular bromine substitution takes place (120°C, DMF, in the presence of a base) for secondary amines (I) yielding aziridines (III). I and III are useful for preparation of the new thion- and imino-thiazolidines containing CF 3 -group [1].

Electronic structure and reactivity of organofluorine compounds

The basicity of isomeric bromoethylamines having a CF3 substituent in the α- and β-positions with respect to the amino group was studied. According to potentiometric titration in H2O, CH3NO2, and CH3CN, the basicity of α-trifluoromethylamines is 4–5 orders of magnitude lower than that of β-trifluoromethyl isomers. Quantum-chemical calculations (AM1) showed that the decrease in the basicity of α-trifluoromethylamines does not correlate with the change in the electron density at the nitrogen atom.

Synthesis of 1-benzyl-2-trifluoromethylaziridine by the Gabriel reaction

Fluorinated aziridines are usually obtained by the addition of diazomethane at a C=N bond [i, 2] or nucleophilic elimination of fluorolefins [3]. The synthesis of nonfluorinated aziridines is often carried out using the Gabriel reaction through cyclization of p-haloalkylamines. In the present work, we have shown that benzylamine adds smoothly to l,l,l-trifluoro-2-bromopropene to form

Influence of α-CF3 and β-CF3 substituents upon the basicities of aliphatic amines

-bromoalkylamine (I). This is the first report of the Gabriel cyclization of (I) for the synthesis of fluoroaziridine (II)~

Influence of α-, β- and γ-cf3-groups upon the kinetics of the Sn2 bromine substitution in alkyl bromides. Role of transition state solvatation

Abstract Dissociation constants (pKa) of the protonated isomeric secondary aliphatic amines (I and II), containing CF 3 -group at, α- or p -position, have been determined by potentiometric titration in H 2 O and CH 3 NO 2 . CF 3 CHBrCH 2 NHR (I, a-c) CF 3 CH(NHR)CH 2 Br (II, a-c) RMe(a), Et(b), Bz(c). The appearance of CF 3 -group at α-position of the amines leads to the sharp decreasing (4-5 orders) of their basicities as compared with the isomeric compounds containing β-CF 3 -groups. Such influence one can naturally explain in terms of the lowering of electronic population on nitrogen atom under the strong inductive effect of CF 3 -group. However surprisingly, the quantum-chemical AM1 calculations show that the total charges on nitrogenes in CF 3 CHBrCH 2 NH 2 (I, d) and CF 3 CH(NH 2 )CH 2 Br (II, d) are equal (−0, 34). The real differences exist in the frontier orbitals energy levels (I, d −10, 30 and −0, 36 eV; II, d −10, 72 and +0, 15 eV), which determine the basicity magnitudes.

Electronic structure and reactivity of organofluorine compounds: 6. The effect of the position of the CF3 group on the basicity of aliphatic amines

Abstract As known the activation barrier rises and the reaction rate decreases for S N 2 halogene substitution in Alk-Hal, containing α-CF 3 substituent. This effect was discussed in terms of destabilization electronic influence of α-CF 3 -group and the increasing of the steric hindrances for S N 2 attach [1,2]. We have investigated the kinetics of the S N 2 bromine substitution in CF 3 (CH 2 ) n Br (n=1,2,3), containing of CF 3 -group at α-, β- and γ-position correspondingly There is the insignificant difference in constant rates for compounds III (k 3 ) and II(k 2 ). However for compound I the magnitude of k 1 fall down sharply. The quantum-chemical calculations(method AM1), polarographic and NQR-spectra studies show the absence of any dramatic differences in charge distribution and energy levels of frontier orbitals for ground states of compound I, and II, III. Moreover, AM1 calculations of transition state of the reaction Br − + RBr show that the appearance of CF 3 -group at α-position of RBr decreases the enthalpy of barrier: ΔH ‡  ΔH(RBr 2 ) ‡  ΔH(Rbr + Br − ); ΔH ‡ for C 2 H 5 Br +4,7 and CF 3 CH 2 Br +3,9, for CH 3 CH 2 CH 2 Br +5,2 and CF 3 CH 2 CH 2 Br +1,6 kcal/mol. However evaluation of solvatation energy contributions (CH 3 CN, e =37) indicates that the increasing of activation barrier and the strong braking effect of αCF 3 group arise from the significant difference between solvatation energies of starting reagents and transition state: ΔH ‡ for CH 3 CH 2 Br +14,7 and CF 3 CH 2 Br +33,1; for CH 3 CH 2 CH 2 Br +16,2 and CF 3 CH 2 CH 2 Br +17,4 kcal/mol.