Synthesis and stereochemistry of cis-2,6-diphenyl-1-alkylpiperidines

[Display omitted] Facile and efficient synthesis of N-alkyl-2,6-diphenylpiperidines (NADPPs) was achieved by reductive amination cyclization (RAC) reaction on 1,5-diketones using alkylammonium formate. The reaction is a useful extension of classical Leuckart reductive amination. The RAC reaction is...

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Bibliographic Details
Published in:Tetrahedron letters 2015-11, Vol.56 (45), p.6190-6193
Main Authors: Rao, H. Surya Prakash, Poonguzhali, Elamvazhuthi
Format: Article
Language:English
Subjects:
2,6-Diphenyl-1-alkylpiperidines
Alkylammonium formate
Leuckart reaction
Microwave
PEG-200
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Summary:[Display omitted] Facile and efficient synthesis of N-alkyl-2,6-diphenylpiperidines (NADPPs) was achieved by reductive amination cyclization (RAC) reaction on 1,5-diketones using alkylammonium formate. The reaction is a useful extension of classical Leuckart reductive amination. The RAC reaction is convenient and product isolation is simple when conducted under microwave (MW) irradiation in polyethylene glycol-200 (PEG-200) medium. The N(1) alkyl groups in NADPPs prefer equatorial position in both solid and liquid states possibly due to favorable CH–π-interactions to evade unfavorable 1,3-diaxial interactions. Incisive analysis of 1H NMR spectra of NADPPs showed that anisotropic effects of C(2) and C(6) phenyl rings are maximum on C(3)H of the alkyl chain.
ISSN:0040-4039
1873-3581
DOI:10.1016/j.tetlet.2015.09.085