Comprehensive synthesis of monohydroxy-cucurbit[n]urils (n = 5, 6, 7, 8): High purity and high conversions

Mehmet M. Ayhan, Hakim Karoui, Micaël Hardy, Antal Rockenbauer, Laurence Charles, Roselyne Rosas, Konstantin Udachin, Paul Tordo, David Bardelang, Olivier Ouari

Research output: Contribution to journalArticle

61 Citations (Scopus)

Abstract

We describe a photochemical method to introduce a single alcohol function directly on cucurbit[n]urils (n = 5, 6, 7, 8) with conversions of the order 95-100% using hydrogen peroxide and UV light. The reaction was easily scaled up to 1 g for CB[6] and CB[7]. Spin trapping of cucurbituril radicals combined with MS experiments allowed us to get insights about the reaction mechanism and characterize CB[5], CB[6], CB[7], and CB[8] monofunctional compounds. Experiments involving 18 O isotopically labeled water indicated that the mechanism was complex and showed signs of both radical and ionic intermediates. DFT calculations allowed estimating the Bond Dissociation Energies (BDEs) of each hydrogen atom type in the CB series, providing an explanation of the higher reactivity of the "equatorial" C-H position of CB[n] compounds. These results also showed that, for CB[8], direct functionalization on the cucurbituril skeleton is more difficult because one of the methylene hydrogen atoms (H b ) has its BDE lowering within the series and coming close to that of H c , thus opening the way to other types of free radicals generated on the CB[8] skeleton leading to several side products. Yet CB[5]-(OH) 1 and CB[8]-(OH) 1 , the first CB[8] derivative, were obtained in excellent yields thanks to the soft method presented here.

Original languageEnglish
Pages (from-to)10238-10245
Number of pages8
JournalJournal of the American Chemical Society
Volume137
Issue number32
DOIs
Publication statusPublished - Aug 19 2015

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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    Ayhan, M. M., Karoui, H., Hardy, M., Rockenbauer, A., Charles, L., Rosas, R., Udachin, K., Tordo, P., Bardelang, D., & Ouari, O. (2015). Comprehensive synthesis of monohydroxy-cucurbit[n]urils (n = 5, 6, 7, 8): High purity and high conversions. Journal of the American Chemical Society, 137(32), 10238-10245. https://doi.org/10.1021/jacs.5b04553