Chemistry of N-nitroso compounds. 1. Synthesis and stereodynamics of N-nitrosopiperidines and N-nitrosopiperidin-4-ones

Mass spectrometry of 1,2,5-oxadiazole N-oxide derivatives: use of deuterated analogues in fragmentation pattern studies

“…The molecular structure of derivative 6-d 1 has been determined by X-ray diffraction methods ( Figure 6). 18,19 In addition, we prepared 6-d 4 , the tetra-deuterium analogue in the 2,6-position of piperazine ring, through reaction between the chloride 3 and the heterocyclic amine 20 which was converted into the tetra-deuterium analogue 16 following the Keefer-Fodor methodology. 21 To transform nitrosamine 16 into amine 17 we tried a procedure by Kano et al (reduction with NaBH 4 :TiCl 4 (2:1) in diglyme) with bad results.…”

“…Compounds 1-3, 1-i, 1-deoxy, 7, 7-deoxy, 15 and 16 were prepared as previously described. 4,6,9,20,21 Elemental analyses were obtained from vacuum-dried samples (over phosphorous pentoxide, 24 h at room temperature) and performed on a Fisons EA 1108 CHNS-O analyzer, and were within ± 0.4% of theoretical values. Infrared spectra were recorded on a Perkin Elmer 1310 apparatus, using potassium bromide tablets; the frequencies are expressed in cm -1 .…”

Synthesis and antimicrobial activities of N-chloroacetyl-2,6-diarylpiperidin-4-ones

“…Generally, the attachment of an electron-withdrawing acyl group (-COR) at the nitrogen site of the 2,6-diarylpiperidin-4-one ring is known to exert a major change in the ring conformation and the chemical shifts of ring carbons and attached protons (Krishnapillai et al, 2000;Krishnakumar and Krishnapillai 1996). These conformational and chemical-shift changes are attributed to the involvement of the lone pair of electrons on the ring nitrogen in conjugation with the -COR function (Chow et al, 1968;Lunazzi et al, 1982;Lunazzi et al, 1980;Ravindran et al, 1991;Senthilkumar et al, 1992;Krishnakumar and Krishnapillay, 1996;Krishnakumar and Krishnapillay, 1992;Krishnapillay et al, 2000;Gdaniec et al, 1995;Rubiralta et al, 1989). Hence, this kind of conjugation creates partial double-bond character about the N-CO bond in 11-20, which in turn leads to restricted rotation about this bond as shown in Scheme 1.…”

Conformational Studies of Some N-Acyl-3- Ethylpiperidin-4-Ones

“…The conformational studies of various 2,6-dimethyl, 2.6-diethyl and 2,6-diphenylpiperidone derivatives [1][2][3][4][5][6][7][8][9] exhibited normal chair conformation. The same type of compounds i.e., 3-isopropylpiperidin-4-one derivatives are prepared and also done conformational studies (Manimekali et al 10) .…”