Abstract
A limited array of reactive intermediates have enabled a wealth of discoveries in N-heterocyclic carbene organocatalysis. In this study, the viability of α,β-unsaturated sulfonyl azoliums as double electrophiles in new reactions is examined. Specifically, the (3+3) annulation of such species with the trimethylsilyl enol ethers of various 1,3-dicarbonyl compounds has been developed. This reaction provides access to a range of novel unsaturated δ-sultones (18 examples) in good yields (40-88 %) under mild reaction conditions. Mechanistic studies and the development of an enantioselective variant (55 % yield, 73:27 e.r.) support the intermediacy of an α,β-unsaturated sulfonyl azolium species. A new intermediate: The coupling of α,β-unsaturated sulfonyl fluorides with silyl enol ethers in the presence of N-heterocyclic carbenes provides δ-sultones in good yields. Various mechanistic studies indicate the formation of an α,β-unsaturated sulfonyl azolium intermediate
Original language | English |
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Pages (from-to) | 11780-11784 |
Number of pages | 5 |
Journal | Angewandte Chemie - International Edition |
Volume | 54 |
Issue number | 40 |
DOIs | |
Publication status | Published - 2015 |
Keywords
- N-heterocyclic carbenes
- nucleophilic catalysis
- organocatalysis
- sulfonyl azolium intermediates
- sulfonyl fluorides