Lack of selectivity in the electrophilic addition of p-toluenesulfonylnitrene to tertiary amines. Conformational equilibrium in N-methylpiperidines

Mechanism of Binding of Fluoroquinolones to the Quinolone Resistance‐Determining Region of DNA Gyrase: Towards an Understanding of the Molecular Basis of Quinolone Resistance

“…This conformation preference is also observed experimentally for the Nmethylpiperidine molecule. [31][32][33][34] Ciprofloxacin, levofloxacin, and moxifloxacin can each exist as three chemical species (cationic, zwitterionic, and anionic) depending on the pH of the aqueous solution. For ciprofloxacin, the experimentally measured pK a1 and pK a2 values are 5.9 and 8.2.…”

Conformational analysis. 39. Carbon-13 NMR spectra of saturated heterocycles. 9. Piperidine and N-methylpiperidine

“…7 It now seems clear that this preference is quite extreme,8-9 amounting to 3.15 ± 0.1 kcal/mol in the gas phase, 2.99 ± 0.1 kcal/mol in dodecane, and 2.41 ± 0.1 kcal/mol in chloroform;10 our own earlier value of 1.35 < AG°<1.77 kcal/mol was evidently too low because of difficulties with the adequacy of the model compounds used in the l3C NMR study. [7][8][9][10][11] The question of the N-H equilibrium in piperidine itself has been even more controversial with some investigators holding that the equatorial position was preferred12 whereas others favored the axial. 13 A recent careful low-temperature NMR study5 gives a -AG°value of 0.36 kcal/mol for the N-H (ae) equilibrium with the equatorial position most likely preferred and an even more recent infrared study of the 8-Zert-butyl-Zra/to-decahydroquinolines1 now leaves no doubt that equatorial N-H is favored.…”

“…If one reasonably assumes33 that conformational energies are additive for nonvicinal substituents, equilibrium data for 9 and 9m (Table VI) along with those for 3m permit calculation of the conformational energy for a 2-methyl substituent in piperidine and 7V-methylpiperidine. Once the latter value is known, data for 8 and 8m in turn permit calculation of the conformational energy for a 4-methyl group.…”

Chemistry of Aminimides

“…c6h5 N-c=o The short distance observed suggested crystal packing forces (54). Studies of aminimides containing the ptoluenesulfonimide group found strong bonds at 1090, 1130, and 1360 cm"1 (10).…”

“…Sulfonyl azides react under photochemical conditions with tertiary amines and form sulfonimides. This reaction has been carried R3N + 4-CH3C6H4S02N3 R3NNS02C6H4CH3-4 out with butyldimethylamine, isobutyldimethylamine, substituted morpholines, piperidine, and tropane (10). If the amine and azide functions are present in the same molecule (9) a cyclic aminimide (10) is formed (107) upon heating.…”