Competitive Ring Expansion of Azetidines into Pyrrolidines and/or Azepanes

Azetidines fitted with a 3-hydroxypropyl side chain at the 2-position undergo intramolecular <i>N</i>-alkylation after activation of the primary alcohol, and the produced 1-azonia-bicyclo­[3.2.0]­heptane is opened by different nucleophiles (cyanide, azide, or acetate anions) to produce mixtures of ring expanded pyrrolidines and azepanes, or a unique type of compound. Distribution of produced five- or seven-membered rings depends on the substitution pattern on the azetidine ring and on its side chain, together with the nature of the nucleophile used in the expansion process. Observed regioselectivities for nucleophilic opening are rationalized by quantum mechanical DFT calculations and are in good agreement with experimental results

4,5-Bis(dimethylamino)quinolines: Proton Sponge versus Azine Behavior

Two first representatives, <b>5</b> and <b>6</b>, of the still unknown 4,5-bis(dimethylamino)quinoline have been synthesized and studied. While the former, being protonated either at the peri-NMe₂ groups or at the ring nitrogen, has been shown to display properties of both a proton sponge and azine, its counterpart <b>6</b> behaves exclusively as azine giving only a quinolinium salt

Charge Transfer Complexes Formed by Heterocyclic Thioamides and Tetracyanoethylene: Experimental and Theoretical Study

Tetracyanoethylene (TCNE) as one of the most versatile organic compounds is involved in various chemical reactions with electron transfer. Charge transfer complexes (CTCs) of a few antioxidants, nitrogen containing thioamides [pyrrolidine-2-thione (<b>I</b>), 1,3-<i>H</i>-imidazolidine-2-thione (<b>II</b>), 1,3-<i>H</i>-Imidazoline-2-thione (<b>III</b>), pyridine-2-thione (<b>IV</b>), 5-trifluoromethylpyridine-2-thione (<b>V</b>), 4-trifluoromethylpyrimidine-2-thione (<b>VI</b>), quinoline-2-thione (<b>VII</b>), 3,4,5,6-tetrahydropyrimidine-2-thione (<b>VIII</b>)] as π-donors and TCNE as π-acceptor were studied. The DFT PCM/UB3LYP/6-31++G­(d,p) and SA-CASSCF quantum chemical calculations were used to study the structures and relative stabilities of these complexes in the ground and lowest excited electronic states. The formation of a weak molecular associates in the chloroform and acetonitrile solutions was confirmed by UV/vis and IR absorption spectroscopy. The stability constants and molar extinction coefficients were estimated by UV/vis spectroscopy. The highest stability in acetonitrile is found for associates formed by quinoline-2-thione and pyridine-2-thione with TCNE, the lowest one is found for CTC formed by imidazolidine-2-thione. Molecular associate formed by pyridine-2-thione and TCNE has the greatest stability in the chloroform solution. 5-Trifluoromethylpyridine-2-thione and 4-trifluoromethylpyrimidine-2-thione do not form CTC in CH₃CN due to the presence of an electron acceptor group in the molecules. The molar extinction values of CTC vary within the range of 0.4 × 10³ to 1.0 × 10⁴ M^–1 cm^–1. An analytical strategy of thioamides identification based on wavelength and intensity of CTCs absorption band has been suggested

4,5-Bis(dimethylamino)quinolines: Proton Sponge versus Azine Behavior

Two first representatives, <b>5</b> and <b>6</b>, of the still unknown 4,5-bis(dimethylamino)quinoline have been synthesized and studied. While the former, being protonated either at the peri-NMe₂ groups or at the ring nitrogen, has been shown to display properties of both a proton sponge and azine, its counterpart <b>6</b> behaves exclusively as azine giving only a quinolinium salt

4,5-Bis(dimethylamino)quinolines: Proton Sponge versus Azine Behavior

Two first representatives, <b>5</b> and <b>6</b>, of the still unknown 4,5-bis(dimethylamino)quinoline have been synthesized and studied. While the former, being protonated either at the peri-NMe₂ groups or at the ring nitrogen, has been shown to display properties of both a proton sponge and azine, its counterpart <b>6</b> behaves exclusively as azine giving only a quinolinium salt