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Ring‐Chain Tautomerism of 3,5‐Disubstituted 5,6,7,8‐Tetrahydro‐3H‐3H‐[1,2,4]oxadiazolo[4,3‐ c ]pyrimidine, a Novel Heterocyclic Ring System
Author(s) -
Korbonits DezsÓ,
TóbiaAsHéja Erzsébet,
Simon KÁLmÁN,
Kolonits PÁL
Publication year - 1991
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19911240931
Subject(s) - tautomer , chemistry , benzaldehyde , oxime , ring (chemistry) , pyrimidine , imine , stereochemistry , medicinal chemistry , organic chemistry , catalysis
The reaction of 3‐aminopropionamide oxime ( 7 ) with two equiv. of benzaldehyde or of a substituted benzaldehyde gives cis ‐3,5‐diaryl‐5,6,7,8‐tetrahydro‐3 H [1,2,4]oxadiazolo[4,3‐ c ]‐pyrimidines ( cis ‐ 11a‐c,e ). According to 1 H‐, 13 C‐, and 15 N‐NMR studies these compounds form in solution a novel triple tautomeric equilibrium comprising cis ‐ and trans ‐ 11a ‐ c, e and 3‐[2‐(benzylidineamino)ethyl]‐5‐ aryl ‐4,5‐dihydro‐1,2,4‐oxaliazoles ( 10a ‐ c, e ). However, the solid obtained from 7 and two equiv. of cinnamaldehyde proved to be an imine ( 10g ), which again formed in solution a similar triple tautomeric system analogously to the mutarotation of sugars. The structure of 11a and 10g was confirmed by X‐ray crystallography.