Premium
Chemistry of the Heterocyclic Pseudobasic Amino Alcohols, XXXVIII Ring‐Chain Tautomerism of Pyrimido[6,1‐ a ]isoquinolines
Author(s) -
Korbonits Dezsö,
Horváth GÁBor,
Simon KÁLmÁN,
Kolonits PÁL
Publication year - 1990
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.19901230315
Subject(s) - chemistry , tautomer , ring (chemistry) , ammonium hydroxide , aqueous solution , hydroxide , ammonium , alkali metal , imine , covalent bond , medicinal chemistry , base (topology) , polymer chemistry , organic chemistry , catalysis , mathematical analysis , mathematics
In basis media, 4‐substituted pyrimido[6,1‐ a ]isoquinolin‐2‐imine hydrochlorides ( 4 ) constitute an equilibrium system involving the tautomeric forms characteristic of pseudobases 5, 6, 7 and the anhydro base 9 . In aqueous solution in the pH range 7–13 the ammonium hydroxide form 5 is present. Between pH 13 and 14 the pseudobase 6 probably arises from this by covalent binding of the hydroxy group. 6 is then converted to the more stable imino type anhydrobase 9 . Ring cleavage of 4 by excess alkali or of 9 by a small amount of water gives 1‐(acylamidinomethylen)isoquinolines 7 . Compounds 7 and 9 are stable in the solid state or in aprotic solutions but revert to cation 5 in dilute protic solutions.