Thiazolium-catalyzed intermolecular Stetter reaction of linear and cyclic alkyl α-diketones.
An efficient method for the N-heterocyclic carbene (NHC)-catalyzed conjugate addition of acetyl anions to various α,β-unsaturated acceptors (Stetter reaction) has been optimized by using 2,3-butandione (biacetyl) as an alternative surrogate of acetaldehyde. The disclosed procedure proved to be compatible with microwave dielectric heating for reaction time reduction and with the use of different linear α-diketones as acyl anion donors (e.g. 3,4-hexanedione for propionyl anion additions). Moreover, the unprecedented umpolung reactivity of cyclic α-diketones in the atom economic nucleophilic acylation of chalcones is herein presented. Mechanistic aspects of the thiazolium-based catalysis involving linear and cyclic α-diketone substrates are also discussed.
Dipartimento di Chimica, Laboratorio di Chimica Organica, Università di Ferrara, Via L. Borsari 46, I-44121, Ferrara, Italy.
Olga
O
Bortolini
Giancarlo
G
Fantin
Marco
M
Fogagnolo
Pier Paolo
PP
Giovannini
Alessandro
A
Massi
Salvatore
S
Pacifico
D002384:Catalysis; D007659:Ketones / Q000138:chemical synthesis* / Q000737:chemistry; D015394:Molecular Structure; D013844:Thiazoles / Q000737:chemistry*
D007659:Ketones; D013844:Thiazoles