Trifluoromethylated oxindoles

Scheme 8.31 Cu(MeCN)4PFg-catalyzed one-pot synthesis of trifluoromethylated oxindoles.

Recently, another novel reaction for the synthesis of trifluoromethylated oxindoles via Cu(N03)2-2.5H20-catalyzed aryl C(sp )-H functionalization was described by Liang, Lipshutz, and coworkers. The trifluoromethylated oxindoles... 

Buchwald reported the same process but as applied to vinyl triflates and nonaflates. In this case, TMSCF3 or TESCF3 was combined with KF or RbF to provide the CF3 anion, which would transfer on to the metal centre. Liu reported the palladium catalyzed indole C-2 trifluoromethylation which is proposed to proceed through a Pd(ii)/Pd(iv) cycle whereby bisacetox-yiodobenzene serves as oxidant.Also reported was the bis-functionalisa-tion of alkenes, specifically resulting in the formation of trifluoromethylated oxindoles (Scheme 15.115). It was found that addition of ytterbium triflate served to increase yields. 

Asymmetric Alkylation. 7Y-[4-(Trifluoromethyl)benzyl]-cinchoninium bromide (1) has been used as chiral phase-transfer catalyst in the alkylation of indanones (eq 1). For the alkylation of a-aryl-substituted carbonyl compounds the diastere-omeric 7Y-[4-(trifluoromethyl)benzyl]cinchonidinium bromide (2) was used to obtain the opposite stereochemistry (eqs 2 and 3). The asymmetric alkylation of oxindoles was used as the key step in an asymmetric synthesis of (—)-physostigmine (eq 4). ... 

The group subsequently found that trifloromethyl ketones and isatins were suitable electrophiles for the NHC-catalysed [2 + 2] cycloaddition reaction of ketenes, ° giving the eorresponding trifluoromethyl-substituted p-lactones 165 and spiroeyelie oxindole-p-laetones 167, respectively, in good yields with high enantioselectivities (Scheme 20.69). 

In 2011, Ye and coworkers found that N-heterocyclic carbene C7 was an efficient catalysts for the cyclisation reaction of a,p-unsaturated p-methylacyl chloride with activated trifluoromethyl ketones or isatin. The spirocyclic oxindole-dihydropyrones 198 and trifluoromethyldihydropyrones 199 were obtained in good yield with good to high enantioselectivity (Scheme 20.84). 

Scheme 39 y-Selective addition of alkylidene oxindoles to p-trifluoromethyl nitroolefins... 

---