02285nas a2200253   4500008004100000022001400041245013800055210006900193260007300262300001000335490000800345520134600353653001101699653001701710653001801727653002001745653002301765653002001788100002901808700002701837700002601864700002101890856012001911       2011                        eng d  a0022-286000aFacile synthesis of N-benzylated 3-alkyl-2,6-diarylpiperidin-4-ones: Stereochemical investigation by 1D/2D NMR and single-crystal XRD0 aFacile synthesis of Nbenzylated 3alkyl26diarylpiperidin4ones Ste  aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcMAR  a44-560 v9903 a<p>A series of thirteen 1-benzyl-3-alkyl-2,6-diarylpiperidin-4-ones 14-26 were conveniently synthesized in high yields 87-92%. In order to find the impact on piperidone stereochemistry, beside the N-benzylation, methyl/ethyl/isopropyl groups at C-3 and halo/alkyl/alkoxy/benzyloxy groups on the phenyl rings at C-2/C-6 were introduced. All the synthesized compounds were characterized by mass, (1)H and (13)C NMR spectral studies. Of them, the 1-benzyl-3-ethyl-2,6-diphenylpiperidin-4-one 22 was completely characterized by 2D NMR techniques such as (1)H-(1)H COSY, (1)H-(13)C COSY and NOESY to assign the signals, unambiguously. The proton coupling constants and NOE correlations provided the complete stereochemistry of 22, which is further witnessed by its single-crystal XRD analysis. The NMR and XRD studies revealed that the compound 22 exists in a chair conformation with equatorial orientation of all the substituents in both solution and solid states. On the basis of their vicinal coupling constants, the chair conformation with equatorial orientation of the substituents at C-2, C-3, C-6 and N is proposed for all compounds 14-26; moreover, a considerable population of boat conformation also suggested for the compound 26 along with the predominant chair conformation, in solution. (C) 2011 Elsevier B.V. All rights reserved.</p>10a2D NMR10aConformation10aN-benzylation10aPiperidin-4-one10asingle-crystal XRD10aStereochemistry1 aDindulkar, Someshwar, D.1 aParthiban, Paramasivam1 aPuranik, Vedavati, G.1 aJeong, Yeon, Tae  uhttps://library.ncl.res.in/content/facile-synthesis-n-benzylated-3-alkyl-26-diarylpiperidin-4-ones-stereochemical-002682nas a2200253   4500008004100000022001400041245007200055210006900127260007300196300001200269490000900281520182000290653002302110653001802133653002202151653001802173653000802191653002002199100002902219700002702248700002602275700002102301856010602322       2012                        eng d  a0022-286000aSynthesis and stereochemistry of highly crowded N-benzylpiperidones0 aSynthesis and stereochemistry of highly crowded Nbenzylpiperidon  aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcJAN  a158-1670 v10073 a<p>A series of N-benzylated 3,5-diakyl-2,6-diarylpiperidin-4-ones 4-8 were conveniently synthesized in significant yields of 68-88% by N-benzylation of the corresponding 2,6-diaryl-3,5-dimethylpiperidin-4-ones 1-3 using different benzyl bromides. Initially, the new piperidone 2,6-bis(4-ethoxypheny1)-3,5-dimethylpiperidin-4-one 3 was synthesized by the condensation of 1:1:2 M ratio of 3-pentanone, ammonium acetate and para-ethoxybenzaldehyde in ethanolic medium. All the synthesized new compounds 3-8 were characterized by their analytical and spectral (IR, H-1 and C-13 NMR) interpretations. The stereochemistry of the new piperidone 3 was elucidated as chair conformation with an equatorial orientation of all substituents, suggested by its vicinal couplings from H-1 NMR spectrum. To investigate the impact on piperidone stereochemistry as well as NMR chemical shifts, all the N-benzylated products 4-8 were compared with their corresponding precursors, and as a result, it is clearly established that all the synthesized N-benzyl piperidones exist in the chair conformation with an equatorial orientation of all the substituents at C-2, C-3, C-5, C-6 and N. Contrary to the probability all N-benzylated compounds retain the same conformation and configuration as their precursors, however, a remarkable change on the chemical shifts are observed. For the further unambiguous confirmation of stereochemistry, the 1-benzyl-3,5-dimethyl-2,6-diphenylpiperidin-4-one 4 was examined by single-crystal X-ray diffraction. The compound 4, C26H27NO, crystallized in a P-1 space group under triclinic system with unit cell dimensions a, b, c (angstrom) and alpha, beta, gamma (degrees) of 10.156(2), 11.002(2), 11.348(4) and 116.74(4), 100.81(3), 100.17(3), respectively. (C) 2011 Elsevier B.V. All rights reserved.</p>10aChair conformation10aConfiguration10acrystal structure10aN-benzylation10aNMR10aPiperidin-4-one1 aDindulkar, Someshwar, D.1 aParthiban, Paramasivam1 aPuranik, Vedavati, G.1 aJeong, Yeon, Tae  uhttps://library.ncl.res.in/content/synthesis-and-stereochemistry-highly-crowded-n-benzylpiperidones-0