Barton esters for initiator-free radical cyclisation with heteroaromatic substitution.
S-(1-Oxido-2-pyridinyl)-1,1,3,3-tetramethylthiouronium hexafluorophosphate (HOTT) facilitates the first examples of efficient radical cyclisation with (hetero)aromatic substitution via Barton ester intermediates. Cyclopropyl and alkyl radicals allow access to five, six and seven-membered alicyclic-ring fused heterocycles with and without an additional fused cyclopropane, including the skeleton of the anti-cancer agent, cyclopropamitosene, expanded, and diazole analogues. Radical initiators are not required for cyclisation from carboxylic acid precursors.
School of Chemistry, National University of Ireland Galway, University Road, Galway, Ireland.
Robert
R
Coyle
Karen
K
Fahey
Fawaz
F
Aldabbagh
D003500:Cyclization; D004952:Esters / Q000737:chemistry*; D005609:Free Radicals / Q000737:chemistry; D006571:Heterocyclic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D006841:Hydrocarbons, Aromatic / Q000138:chemical synthesis* / Q000737:chemistry; D015394:Molecular Structure
D004952:Esters; D005609:Free Radicals; D006571:Heterocyclic Compounds; D006841:Hydrocarbons, Aromatic