Natural abundance <sup>17</sup>O NMR spectroscopic study of quinone methides

Boykin, David W.; Kumar, Arvind; Shevchenko, S. M.

doi:10.1002/mrc.1260300105

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1996

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Cited by 10 publications

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“…On the other hand, a remarkable shielding ( ca. 80 ppm) is observed when comparing 1f with some enamine ketones …”

Section: Discussionmentioning

confidence: 97%

Cyclobutene-1,2-diones. A Theoretical and Spectroscopic Study

et al. 1996

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The properties of substituted cyclobutene-1,2-diones 1 are examined by the use of (17)O 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 (17)O chemical shifts reproduce the measured trends. The dianions of squaric and deltic acids are highly stabilized by negative charge delocalization to the oxygens.

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“…On the other hand, a remarkable shielding ( ca. 80 ppm) is observed when comparing 1f with some enamine ketones …”

Section: Discussionmentioning

confidence: 97%