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Paper | Regular issue | Vol 29, No. 11, 1989, pp.2185-2192
Published online, 1st January, 1970
DOI: 10.3987/COM-89-5157
13C Dynamic Nmr Studies on Restricted Rotation about C-N Bond in 2-Aryl-1-formyl-4-piperidones

Mario Rubiralta,* M. Pilar Marco, Miguel Feliz, and Ernest Giralt

*Laboratory of Organic Chemistry, Faculty of Pharmacy, University of Barcelona, Av. de Joan XXIII, s/n, 08028 Barcelona, Spain


The synthesis of 1-formyl-2-(3-indolyl)-4-piperidone (7). trans-1-formyl-2-(3-indolyl)-3-methyl-4-piperidone (8), and their 4,4-ethyleneacetals 5 and 6 is described. The introduction of a formyl group on the piperidone nitrogen induces a change in the piperidine ring conformation such that the 2-indoiyl group is axial. However, in the 1-formyl-2-indolyl-4-piperidone 4,4-ethyleneacetals the indolyl group adopts an equatorial disposition due to a severe steric syn-diaxial interaction with the C-4 substituent. 13C-Dnmr is used to investigate the amide rotational barriers in a series of 2-aryl-1-formyl-4-piperidones.