ChemInform Abstract: The Synthesis and Vasopressin (AVP) Antagonist Activity of a Novel Series of N‐Aroyl‐2,4,5,6‐tetrahydropyrazolo[3,4‐d]thieno[3,2‐b]azepines.

Albright, J. Donald; Santos, Efren G. Delos; Dusza, John P.; Chan, Peter S.; Coupet, Joseph; Ru, Xun; Mazandarani, Hossein

doi:10.1002/chin.200030143

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“…1 Most of the piperidine precursors are known to exist in chair conformation. Electron withdrawing groups (-NO, -CHO, -COR and -CONHPh) introduced at the nitrogen atom profoundly affect the conformations of the heterocyclic rings and orientations of the substituents in 2,6-dialkyl-and 2,6-diaryl-substituted piperidines 2-4 due to A 1,3 strain in the normal chair conformation.…”

Section: Introductionmentioning

confidence: 99%

Conformation of hindered piperidines: Spectroscopic evidence for contribution of boat conformations

2010

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High resolution 1 H and 13 C NMR resonance assignments and conformational assignments were carried out for four t(3)-benzyl-r(2),c(6)-bis(aryl)piperidin-4-ones 1-4 and their four N-nitroso-t(3)-benzyl-r(2),c(6)-bis(aryl)piperidin-4-ones 5-8. In addition to conventional 1D NMR methods, 2D shiftcorrelated NMR techniques ( 1 H-1 H COSY and 1 H-13 C COSY) were used for signal assignments. At room temperature the t(3)-benzyl-r(2),c(6)-bis(aryl)piperidin-4-ones 1-4 exist in only one isomeric form whereas their N-nitroso derivatives 5-8 exist in two isomeric forms. The preferred conformations of both the isomeric forms of nitrosamines were determined by comparison of the spectral data with those of the corresponding parent amines 1-4 and with the aid of substituent parameters. The results indicate the presence of an equilibrium mixture of boat forms B 1 and B 2 for Z isomers of 5-8. For the E isomers of 5-8, boat form B 1 is predicted to be the major conformer. The piperidin-4-ones 1-4 exist in normal chair conformations with equatorial orientations of all the substituents.

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Section: Introductionmentioning

confidence: 99%