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Monitoring structural transformations in crystals. 11. Yang photocyclizations - one type of reaction, but diversity of structural changes

TitleMonitoring structural transformations in crystals. 11. Yang photocyclizations - one type of reaction, but diversity of structural changes
Publication TypeJournal Article
Year of Publication2007
AuthorsTurowska-Tyrk, I, Bakowicz, J, Scheffer, JR
JournalActa Crystallographica Section B-Structural Science
Volume63
Pagination933-940
Date PublishedDec
ISBN Number0108-7681
Abstract

Structural changes proceeding in a crystal during the Yang photocyclization of the salt 6,6-diethyl-5-oxo-5,6,7,8-tetrahydronaphthalene-2- carboxylate with (1S)-1-(4-methylphenyl)ethylamine were monitored by means of X-ray structure analysis. The course of the photoreaction was evaluated on the basis of the geometrical parameters for the pure reactant crystal. Variations in the cell constants, the product content, the geometry of the reaction centre, the orientation of molecular fragments and the geometry of hydrogen bonds were described and analyzed. It was found that the cell volume increased until 56% product content and decreased thereafter. The distance between the directly reacting C atoms was constant, similar to 3.0 A S, until similar to 75% reaction progress. Analysis of the distance between atoms that would participate in the formation of the second ( unobserved) enantiomorph excluded the formation of such an isomer. Molecular fragments varied their orientation during the photoreaction, and the largest change was observed for the carboxylate group despite its participation in strong hydrogen bonds. The geometry of the hydrogen bonds changed during the photoreaction. The largest change was 0.17 A S for the D center dot center dot center dot A distance and 13 degrees for the D-H center dot center dot center dot A angle. A comparison of the intra- and intermolecular parameters for the studied salt with data for other compounds undergoing the Yang photocyclization in crystals revealed a diversity of structural changes brought about by this type of photochemical reaction.

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