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Nitrogen bridgehead compounds. Part 76 Synthesis and stereochemistry of ethyl 9‐benzylidene‐6,7,8,9‐tetrahydro‐2‐oxo‐2 H ‐ and 4‐oxo‐4 H ‐pyrido[1,2‐ a ]pyrimidine‐3‐carboxylates and their homologues
Author(s) -
Sipos Judit,
Podányi Benjamin,
Hermecz István,
Pusztay Levente,
Tóth Gábor,
Szilágyi László
Publication year - 1989
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.5570260428
Subject(s) - chemistry , benzaldehyde , piperidine , benzene , ring (chemistry) , condensation , pyrimidine , chemical shift , nitrogen , medicinal chemistry , proton nmr , organic chemistry , stereochemistry , catalysis , physics , thermodynamics
Ethyl 4‐oxo‐6,7,8,9‐tetrahydro‐4 H ‐pyrido[1,2‐ a ]pyrimidine‐3‐carboxylates 1–4 , their piperidine ring homologues 5–6 and their 2‐oxo isomers 7–9 were reacted with benzaldehyde. At low temperature, kinetically stable addition products were formed. Thermodynamically stable condensation products were obtained at higher temperature, which were also formed when the addition products were refluxed in benzene. The 9‐benzyl derivatives were prepared by the hydrogenation of the condensation products over Pd/C. The stereochemical features of the new compounds were determined via 1 H and 13 C nmr chemical shift and coupling constant analysis and NOE measurements.