Oxazolidines from the reaction of (-) ephedrine and (+) pseudoephedrine with salicylaldehyde and p-hydroxybenzaldehyde and their rates of hydrolysis

The rates of hydrolysis of oxazolidines with ortho-hydroxyphenyl substituents at C(2) are more than 30 times faster than oxazolidines with para-hydroxyphenyl substituents. The later rates are identical to those with a phenyl group at C(2) indicating the ortho-hydroxyl orientation is responsible for...

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Bibliographic Details
Published in:Journal of chemical crystallography 1997, Vol.27 (1), p.35-44
Main Authors: BOURNE, S. A, FITZ, L. D, KASHYAP, R. P, KRAWIEC, M, WALKER, R. B, WATSON, W. H, WILLIAMS, L. M
Format: Article
Language:English
Subjects:
Acceleration
Bifurcations
Chemistry
Condensed matter: structure, mechanical and thermal properties
Ephedrine
Exact sciences and technology
Heterocyclic compounds
Heterocyclic compounds with n hetero atom and also o and/or s, se, te hetero atoms
Hydrogen bonds
Hydrolysis
Hydroxybenzaldehydes
Hydroxyl groups
Organic chemistry
Organic compounds
Oxazolidine
Physics
Preparations and properties
Protonation
Structure of solids and liquids
crystallography
Structure of specific crystalline solids
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Summary:The rates of hydrolysis of oxazolidines with ortho-hydroxyphenyl substituents at C(2) are more than 30 times faster than oxazolidines with para-hydroxyphenyl substituents. The later rates are identical to those with a phenyl group at C(2) indicating the ortho-hydroxyl orientation is responsible for the acceleration. In the solid state the ortho-hydroxyl group is hydrogen bonded to the ring nitrogen atom. Since the rate determining step probably involves protonation of the ring oxygen atom and ring cleavage, the rates of reaction are rationalized by a reorientation of the hydrogen bond to the ring oxygen after protonation of the ring nitrogen atom. This involves a movement of less than 1 Å. A bifurcated hydrogen bond is an alternate but related possibility.
ISSN:1074-1542
1572-8854
DOI:10.1007/BF03543085