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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

✍ Scribed by Jan Světlík; Tibor Liptaj; FrantiŠEk Tureček

Publisher: Journal of Heterocyclic Chemistry
Year: 1999
Tongue: English
Weight: 406 KB
Volume: 36
Category: Article
ISSN: 0022-152X
DOI: 10.1002/jhet.5570360132

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✦ Synopsis

Abstract

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.

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