Michael Nguyen, Marilyn Brooks, Emily O’Loughlin, Edward J. Valente
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引用次数: 0
Abstract
Many 4- and 5-oxocarboxylic acids show open-cyclic solution racemization/tautomerism including the dehydration-resistant arylpyran pseudoacid 3-hydroxy-4,4-dimethylisobenzopyran-1-one. The crystal and molecular structures of nine α-anomeric derivatives (including 11 distinct molecular structures) of this pseudoacid (or close analogs) have been determined, including pseudoacyl chlorides, normal, pseudoanhydrides, a dipseudoanhydride, and a tertiary pseudoamide. The basicity of the implied exocyclic leaving groups span 40 pK units. Together with seven closely related pseudoacid molecular structures previously determined, a data set containing 18 compounds was generated. Exocyclic C–O bonds shortened as endocyclic C–O bonds lengthened in linear functions of exocyclic leaving group basicity with l(xC-O, Å) = 1.4426 − 0.00400 * pKa, N = 13, R2 = 0.969; l(nC-O, Å) = 1.4204 + 0.00205 * pKa, N = 18, R2 = 0.951. These correlations were compared with results for other α-anomeric pyranoid systems, tetrahydropyran and dihydropyran, and an arylfuran pseudoacyl system. Exocyclic substituents effectively modified endocyclic C–O bond polarities over a considerable range.
期刊介绍:
Structural Chemistry is an international forum for the publication of peer-reviewed original research papers that cover the condensed and gaseous states of matter and involve numerous techniques for the determination of structure and energetics, their results, and the conclusions derived from these studies. The journal overcomes the unnatural separation in the current literature among the areas of structure determination, energetics, and applications, as well as builds a bridge to other chemical disciplines. Ist comprehensive coverage encompasses broad discussion of results, observation of relationships among various properties, and the description and application of structure and energy information in all domains of chemistry.
We welcome the broadest range of accounts of research in structural chemistry involving the discussion of methodologies and structures,experimental, theoretical, and computational, and their combinations. We encourage discussions of structural information collected for their chemicaland biological significance.