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Please login to access the full content or check if you have access via1.1.15.6.4 Catalytic Generation of α,β-Unsaturated Acyl Azoliums from Acyl Fluorides or Esters
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Chiang, P. -C.; Bode, J. W., Science of Synthesis: Asymmetric Organocatalysis, (2012) 1, 668.
The α,β-unsaturated acyl azolium species described in Section 1.1.15.5.2 can also be generated from acyl fluorides or lactones in a process that does not involve a redox reaction for formation of the key reactive species. Acyl fluorides and enol silanes undergo N-heterocyclic carbene promoted coupling to give dihydropyranones (Scheme 40).[107] This reaction can proceed through conjugate addition of the enolate to the acyl azolium or by a Coates–Claisen process as discussed in Section 1.1.15.5.2. Vinyl esters undergo similar reactions, as would be expected from the nature of the two mechanisms.[108] In these cases, the addition of the N-heterocyclic carbene catalyst to the ester leads to generation of α,β-unsaturated acyl azolium reactive species that undergo C—C bond formation.
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References
[107] | Meee, M. M.; Meeeeee, M.; Meeeee, M. M., M. Me. Meee. Mee., (8888) 888, 88888. |
[108] | Meeeeee, M.; Meeeee, M. M., Mee. Meee., (8888) 88, 8888. |
[109] | Meee, M. M.; Meeeeee, M.; Meeeee, M. M., M. Me. Meee. Mee., (8888) 888, 8888. |