Cyclobutene-1,2-diones. A Theoretical and Spectroscopic Study
- 1 January 1996
- journal article
- Published by American Chemical Society (ACS) in The Journal of Organic Chemistry
- Vol. 61 (18) , 6212-6217
- https://doi.org/10.1021/jo960484a
Abstract
The properties of substituted cyclobutene-1,2-diones 1 are examined by the use of 17O NMR spectroscopy and theoretical calculations and compared to those of cyclopropenones 2 and other models. Cyclobutene-1,2-diones have less negative charge per oxygen compared to cyclopropenones, and electron donation by substituents enhances the negative charge on oxygen. Calculated 17O chemical shifts reproduce the measured trends. The dianions of squaric and deltic acids are highly stabilized by negative charge delocalization to the oxygens.Keywords
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