P-trifluoromethyl enones

Subsequently, the same group reported a synthetically useful protocol to stereospecific synthesis of syn- and a/rti-dihydropyranones containing a stereogenic trifluoromethyl substituent through NHC-catalyzed redox het-ero-Diels-Alder reactions of either E- or Z-p-trifluoromethyl enones with a-aroyloxyaldehydes. Kinetic experiments revealed the formation of 0-acylated enolate species when an achiral precatalyst was used in these reactions, accounting for the difference in reactivity observed compared with a chiral precatalyst. The measurement of a positive KIE suggests that deprotonation of the NHC-aldehyde adduct to form the Breslow intermediate is kinetically significant (Scheme 7.84). 

Scheme 7.84 NHC-catalyzed asymmetric formal Diels-Alder reaction of a-aroy-loxyaldehydes and p-trifluoromethyl enones reported by Smith.

Jeon SL, Kim JK, Son JB, Kim BT, Jeong IH (2007) One pot synthesis of novel a, P-dichloro-P-trifluoromethylated enones and their application to the synthesis of trifluoromethylated heterocycles. J Fluor Chem 128 153-157... 

---

See also in sourсe #XX -- [ ]

---