Palladium trifluoromethyl derivatives

Trifluoroalanine has also been prepared by reducing trifluoropyruvate imines (ethyl trifluoropyruvate is available commercially it is prepared either from per-fluoropropene oxide or by trifluoromethylation of ethyl or f-butyl oxalate). These imines are obtained by dehydration of the corresponding aminals or by Staudinger reaction. They can also be obtained by palladium-catalyzed carbonylation of trifluoroacetamidoyl iodide, an easily accessible compound (cf. Chapter 3) (Figure 5.4). Reduction of the imines affords protected trifluoroalanines. When the imine is derived from a-phenyl ethyl amine, an intramolecular hydride transfer affords the regioisomer imine, which can further be hydrolyzed into trifluoroalanine. ... 

Similarly, Uneyama and Watanabe (91TL1459) have reported the synthesis of trifluoromethylated AI-aryl-1-azabutadienes by palladium-catalyzed coupling of trifluoroacetimidoyl iodides with alkenes as well as the transformation of the azadiene derived from methyl acrylate into the corresponding 4-methoxycarbonyl-2-trifluoromethylquinoline in quantitative yield. 

Dehydrobromination of bromotrifluoropropene affords the more expensive trifluoropropyne [237], which was metallated in situ and trapped with an aldehyde in the TIT group s [238]synthesis of 2,6-dideoxy-6,6,6-trifluorosugars (Eq. 77). Allylic alcohols derived from adducts of this type have been transformed into trifluoromethyl lactones via [3,3] -Claisen rearrangements and subsequent iodolactonisation [239]. Relatively weak bases such as hydroxide anion can be used to perform the dehydrobromination and when the alkyne is generated in the presence of nucleophilic species, addition usually follows. Trifluoromethyl enol ethers were prepared (stereoselectively) in this way (Eq. 78) the key intermediate is presumably a transient vinyl carbanion which protonates before defluorination can occur [240]. Palladium(II)-catalysed alkenylation or aryla-tion then proceeds [241]. 

Planar chiral phosphaferrocene-oxazolines (379) constitute another family of complexes that are usefiil as ligands in asymmetric catalysis. Preparation of these takes advantage of a modified Friedel-Crafts acylation of (373) and an unusual conversion of the resulting trifluoromethyl ketone into an amide that is then cyclized to an oxazoline. The diastereomeric complexes thus formed are chromatographically separable and are used in a palladium-catalyzed asymmetric allylic substitution. Modification of this complex by using the anion derived from 3,4-dimethyl-2-phenylphosphole gives more... 

Various trifluoromethylated metalloporphyrins 54 were prepared in high yields by the reaction of brominated metalloporphyrins 53 (copper and nickel complexes) with stoichiometric amounts of FS02CF2C00Me/CuI in the presence of catalytic amounts of a palladium catalyst [28]. Similarly, the (CF3)2Cd-CF3CdBr-CuBr system was used as a source of trifluoromethyl anion in the synthesis of some porphyrin derivatives [29]. 

Palladium-catalyzed reaction of 5-aryl-2-(trifluoromethyl)furan-3-carbonyl chloride 263 with phenylacetylene afforded derivative 264 which is a convenient precursor for synthesis of pyrazoles, pyrimidines, and other heterocyclic systems bearing trifluoromethylated furan as substituent [154]. 

Inokuchi E, Narumi T, Niida A, Kobayashi K, Tomita K, Oishi S, Ohno H, Fujii N. Efficient synthesis of trifluoromethyl and related trisubstituted alkene dipeptide isosteres by palladium-catalyzed carbonylation of amino acid derived allyUc carbonates. J. Org. Chem. 2008 73 3942-3945. 

Hanzawa Y, Ishizawa S, Kobayashi Y. Palladium(O)-catalyzed reactions of trifluoromethylated allylic ester derivatives synthesis of trifluoromethylated chrysanthemic acid ester. Chem. Pharm. Bull. 1988 36 4209-4211. 

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