Titania-promoted carboxylic acid alkylations of alkenes and cascade addition-cyclizations

David W. Manley*, Roy T. McBurney, Phillip Miller, John C. Walton, Andrew Mills, Christopher O'Rourke

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

44 Citations (Scopus)
12 Downloads (Pure)

Abstract

Photochemical reactions employing TiO2 and carboxylic acids under dry anaerobic conditions led to several types of C-C bond-forming processes with electron-deficient alkenes. The efficiency of alkylation varied appreciably with substituents in the carboxylic acids. The reactions of aryloxyacetic acids with maleimides resulted in a cascade process in which a pyrrolochromene derivative accompanied the alkylated succinimide. The selectivity for one or other of these products could be tuned to some extent by employing the photoredox catalyst under different conditions. Aryloxyacetic acids adapted for intramolecular ring closures by inclusion of 2-alkenyl, 2-aryl, or 2-oximinyl functionality reacted rather poorly. Profiles of reactant consumption and product formation for these systems were obtained by an in situ NMR monitoring technique. An array of different catalyst forms were tested for efficiency and ease of use. The proposed mechanism, involving hole capture at the TiO2 surface by the carboxylates followed by CO2 loss, was supported by EPR spectroscopic evidence of the intermediates. Deuterium labeling indicated that the titania likely donates protons from surface hydroxyl groups as well as supplying electrons and holes, thus acting as both a catalyst and a reaction partner.

Original languageEnglish
Pages (from-to)1386-1398
Number of pages13
JournalJournal of Organic Chemistry
Volume79
Issue number3
DOIs
Publication statusPublished - 7 Feb 2014
Externally publishedYes

Bibliographical note

Copyright the Publisher 2014. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.

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