Diastereoselective synthesis electrophilic fluorination

Mohar B, Sterk D, Ferron L, Cahard D. Enantioselective and diastereoselective synthesis of fluorinated dipeptides by late electrophilic fluorination. Tetrahedron Lett. 2005 46 5029-5031. 

Enders D, Faure S, Potthoff M, Runsink J (2001) Diastereoselective electrophilic fluorination of enantiopure a-silylketones using N-fluoro-benzosulfoni-mide regio- and enantioselective synthesis of a-fluoroketones. Synthesis 2001 2307-2319... 

Konas, D.W. Coward, J.K. Electrophilic fluorination of pyroglutamic acid derivatives application of substrate-dependent reactivity and diastereoselectivity to the synthesis of optically active 4-fluoroglutamic acids. J. Org. Chem. 2001, 66, 8831-8842. 

An interesting catalytic diastereo- and enantioselective tandem transformation via Nazarov cyclization /electrophilic fluorination has been efficiently promoted by a (/ ,/ )-Ph-BOX-Cu(II) complex to afford fluorine-containing 1-indanone derivatives with two new stereocenters with high diastereoselectivity trans/cis up to 49/1) and moderate-to-high enantioselectivities (up to 95.5% ee) (Scheme 44.24). This catalytic enantioselective tandem transformation can be used for synthesis of organofluorine compounds with adjacent carbon- and fluorine-substituted tertiary and quaternary stereocenters. " ... 

From a non-c ohydrate precursor, Davis and Qi achieved the asymmetric synthesis of 2-deoxy-2-fluoro- iylo-D-pyranose (9) (Figure 7) and 2-deoxy-2-fluoro-lyxo-L-pyranose (13). TTie key reaction was the highly diastereoselective fluorination of a chiral enolate using the electrophilic fluorinating agent, N-fluoro(benzenesulfonimide) (NFSi). In another study by Davis (14), the use of a chiral oxazolidinone adjuvant and fluorination with NFSi led to the chiral fluorohydrin 10 (>97% ee), which was oxidized by the Dess-Martin periodinane procedure to the non-racemic a- fluoroaldehyde 11 (94% ee). Conversion of 11 in four steps provided l,2,3-tri-0-acetyl-4-deoxy-4-fluoro-D-arabinopyranose (12) as a 1 1 mixture of anomers which could not be separated by flash chromatography. 

We developed a new easy and versatile diastereoselective synthesis of these amino alcohols. Our synthetic plan was based on the ring opening of trifluoromethyl epoxy ethers 3, which are easily available in two steps from the cheap ethyl trifluoroacetate, and are useful building blocks. The first step, the Wittig olefination of this ester, is possible because of the increased electrophilicity of the ester carbonyl by the fluorinated moiety (Scheme... 

---