Potassium enolate, trifluoromethylations

Trifluoromethylation of Potassium Enolate. Trifluoromethylation of potassium enolate of cyclohexanone )flelds Q -(trifluoromethyl)cyclohexanone in the presence of 2-phenyl-1,3,2-benzodioxaborole (eq 23). The boron compound complex and enolate anion increase the reactivity. 

An efficient synthetic sequence for the preparation of 2,4-b/s(trifluoromethyl)furan was developed by R. Filler and co-workers. " The potassium enolate of ethyl 4,4,4-trifluoroacetate was reacted with 3-bromo-1,1,1-trifluoroacetate in DMSO to afford 2,4-bis (trifluormethyl)-4-hydroxydihydro-3-furoate as a result of O-alkylation. Interestingly, under these conditions usually C-alkylation is preferred. Next, dehydration was performed to give the corresponding 2,4-bis (trifluoromethyl)-3-furoate in good yield. Finally, decarboxylation by heating with quinoline and CUSO4 yielded the target furan in excellent yield. 

In the case of the reaction of cyclohexanone potassium enolate in the presence of the boron complexing agent (50), the selenium reagent (47) appeared to be significantly less efficient as a regioselective trifluoromethylation agent than the sulfur reagent (46). ... 

In tetrakis(trifluoromethyl)allene (9), potassium permanganate in acetonitrile hydroxylates only one C = C bond 93 the resulting enol tautomerizes to an a-hydroxy ketone 10. The reaction has been repeated and extended to other perfluoroalkylated allenes92 achieving yields of 51-60%. 

Benzaldehyde reacts with trimethyl(pcrfluorophenyl)silane/potassium fluoride in a fashion similar to that described by Olah for trimethyl(trifluoromethyl)silanc, togive(perfluorophenyl)-phenyl(trimethylsiloxy)methane.In the absence of potassium fluoride the reaction requires a temperature of 170 C. Other nucleophiles, such as cyanide, in place of fluoride cause trimethyl(perfluorophenyl)silane to react with ketones to produce silyl enol ethers which result from abstraction of an a-hydrogen by... 

---