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

Download
  1. (PDF, 790 KB)
  2. Get@NRC: Comprehensive synthesis of monohydroxy-cucurbit[n]urils (n = 5, 6, 7, 8): High purity and high conversions (Opens in a new window)
DOIResolve DOI: http://doi.org/10.1021/jacs.5b04553
AuthorSearch for: ; Search for: ; Search for: ; Search for: ; Search for: ; Search for: ; Search for: ; Search for: ; Search for: ; Search for:
TypeArticle
Journal titleJournal of the American Chemical Society
ISSN0002-7863
Volume137
Issue32
Pages1023810245; # of pages: 8
SubjectAtoms; Free radicals; Bond dissociation energies; Functionalizations; High conversions; Ionic intermediates; Isotopically labeled; Monofunctional compounds; Photochemical method; Reaction mechanism; Musculoskeletal system
AbstractWe 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 18O 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<inf>b</inf>) has its BDE lowering within the series and coming close to that of H<inf>c</inf>, 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)<inf>1</inf> and CB[8]-(OH)<inf>1</inf>, the first CB[8] derivative, were obtained in excellent yields thanks to the soft method presented here.
Publication date
PublisherAmerican Chemical Society
LanguageEnglish
AffiliationNational Research Council Canada
Peer reviewedYes
NPARC number21277027
Export citationExport as RIS
Report a correctionReport a correction
Record identifier89a96c12-5ae7-4e68-a702-78205786d79f
Record created2015-11-10
Record modified2016-05-09
Bookmark and share
  • Share this page with Facebook (Opens in a new window)
  • Share this page with Twitter (Opens in a new window)
  • Share this page with Google+ (Opens in a new window)
  • Share this page with Delicious (Opens in a new window)