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Conformationally locked heterocycles. Structure of a doubly bridged pyrimido[1,2‐ a ]pyrimidine from the hantzsch synthesis with 4‐(2‐hydroxyphenyl)but‐3‐en‐2‐one
Author(s) -
Světlík Jan,
Liptaj Tibor,
Tureček FrantiŠEk
Publication year - 1999
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.5570360132
Subject(s) - chemistry , pyrimidine , cyanamide , derivative (finance) , stereochemistry , nuclear magnetic resonance spectroscopy , computational chemistry , medicinal chemistry , organic chemistry , financial economics , economics
1D and 2D nmr spectroscopy was used to assign the structure to the minor product from cyclocondensation of 4‐(2‐hydroxyphenyl)but‐3‐en‐2‐one with cyanamide, which was identified as (6 R *, 9 R* , 15 R *, 17 R *)‐6,9‐dimethyl‐6,17:9,15‐dimemano‐6 H ,15 H ,17 H ‐[1,3,5]benzoxadiazocino[4,5‐ d ][1,3,5]benzoxadiazocine‐7(9 H )‐carbonitrile, a doubly oxygen‐bridged pyrimido[1,2‐ a ]pyrimidine derivative. The observed stereose lectivity and reaction mechanisms are discussed with the help of molecular mechanics and semi‐empirical PM3 calculations.