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Experimental and computational evidence for alpha-lactone intermediates in the addition of aqueous bromine to disodium dimethyl-maleate and -fumarate


Reference:

Pirinccioglu, N., Robinson, J. J., Mahon, M. F., Buchanan, J. G. and Williams, I. H., 2007. Experimental and computational evidence for alpha-lactone intermediates in the addition of aqueous bromine to disodium dimethyl-maleate and -fumarate. Organic and Biomolecular Chemistry, 5 (24), pp. 4001-4009.

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Abstract

Structural analysis of the bromo-beta-lactones obtained by addition of bromine to aqueous solutions of disodium 2,3-dimethylmaleate and 2,3-dimethylfumarate reveals stereochemistries opposite to those originally assigned in 1937: cis alkene yields erythro lactone, and trans alkene yields threo lactone. B3LYP/6-31+G(d) calculations using a PCM description of aqueous solvation confirm the validity of our proposed mechanism, in which the first-formed intermediate in each case is an a-lactone. The cyclic bromonium species is not an intermediate. An alternative pathway leading directly from cis alkene to cis lactone, via an unusual frontside displacement mechanism, is over 20 kJ mol(-1) higher in free energy. Hydrolysis of the bromo-beta-lactones yields bromohydrins whose stereochemistries as determined by X-ray crystallography indicate stereospecific formation by acyl-oxygen cleavage of the lactone ring, again contrary to the original view.

Details

Item Type Articles
CreatorsPirinccioglu, N., Robinson, J. J., Mahon, M. F., Buchanan, J. G. and Williams, I. H.
DOI10.1039/b711538e
DepartmentsFaculty of Science > Chemistry
RefereedYes
StatusPublished
ID Code4553
Additional InformationID number: ISI:000251274700016

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