171503-48-3Relevant academic research and scientific papers
Generation and carbonyl addition reactions of dibromofluoromethyllithium derived from tribromofluoromethane as applied to the stereoselective synthesis of fluoro olefins and 2-bromo-2-fluoro-1,3-alkanediols
Shimizu, Masaki,Yamada, Nobuko,Takebe, Yoko,Hata, Takeshi,Kuroboshi, Manabu,Hiyama, Tamejiro
, p. 2903 - 2921 (2007/10/03)
The treatment of tribromofluoromethane with BuLi in THF-Et2O (2: 1) at - 130°C generated dibromofluoromethyllithium, which was allowed to react smoothly with a coexisting aldehyde or ketone (RR'C=O) to give fluorinated alcohol RR'C(OH)CFBr2 (3) in good yield. Alcohol 3 was converted stereoselectively to (E)-1-bromo-1,2-difluoro olefin 5 via fluorination with Et2NSF3, followed by dehydrobromination with lithium 2,2,6,6- tetramethylpiperidide, while (E)-1-bromo-1-fluoro olefin was obtained with high selectivity by acetylation of 3, followed by reductive elimination using EtMgBr/(i-Pr)2NH. Difluoro olefin 5 underwent a cross-coupling reaction with an aryl, alkenyl, or alkynylmetal reagent to afford the corresponding fluoro olefin with retention of configuration. On the other hand, the treatment of RCH[OCH2O(CH2)2OCH3]CFBr2 with BuLi at -130°C in the presence of 4- heptanone gave the corresponding adduct diastereoselectively. The stereochemical outcome is explained in terms of chelation between lithium and oxygen atoms of the (2-methoxyethoxy)methyl group. Starting with 2- phenylpropanal, a product is obtained highly selectively containing three contiguous stereocenters including a -CFBr-moiety.
