Highly Stereocontrolled Synthesis of Trifluoromethylated Materials with Allylzincs and Allenylzincs Generated by Umpolung of Palladium Complexes

Abstract

The formation and chemical behaviors of trifluoromethylated allylzinc and allenylzinc reagents derived from the umpolung of allyl- or allenylpalladium complexes have been described. The reactions of these reagents with aldehydes proceeded smoothly to afford highly stereocontrolled γ-(trifluoromethyl)-δ-hydroxy α,β-unsaturated materials. Their configurations determined by the spectral data were anti, and Z-isomers were produced from the system of allylzinc reagents.

Stereoselective Construction of an Asymmetric Carbon Center Possessing a Trifluoromethyl Group

“…Kitazume et al have reported that allylzinc species can generate efficiently from -trifluoromethylated allyl carbonate, and react with various aldehydes in a highly diastereoselective manner (Scheme 49) [117]. Thus, treatment of -trifluoromethylated allyl carbonates 183 with Pd(PPh 3 ) 4 gives the corresponding electrophilic -allylpalladium complex 184, which can react with Et 2 Zn to provide the nucleophilic allylzinc complex 185 in situ, as well as to regenerate Pd(0) species.…”

Highly Diastereoselective Aldol Reaction with α‐CF3‐Substituted Enolates

“…The observed coupling constant between H a and H b of the acetonide 4 a was <1 Hz, as expected for an H ax ,H eq coupling constant in such an acetonide 7. It is also important to note that the anti acetonide with a phenyl group (instead of a 4‐nitrophenyl moiety) has already been prepared by a different approach, and showed a different and typical H ax ,H ax coupling constant of 10 Hz 8…”

Synthesis of stereocontrolled α,α-difluoro-β-hydroxycarbonyl materials

“…In our continuous study of stereocontrolled fluorinated materials [12], we would like to describe a practical enzymatic method for a,a-difluoro-b-hydroxy-g,d-unsaturated carbonyl materials with high optical purity in a large scale handling. The absolute configuration of the obtained a,a-difluoro-b-hydroxy-g,d-unsaturated carbonyl materials was determined by the modified Mosher's method with NMR spectral data.…”