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

Citation
M. Shimizu et al., 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, B CHEM S J, 71(12), 1998, pp. 2903-2921
Citations number
115
Language
INGLESE
art.tipo
Review
Categorie Soggetti
Chemistry
Journal title
BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN
ISSN journal
0009-2673 → ACNP
Volume
71
Issue
12
Year of publication
1998
Pages
2903 - 2921
Database
ISI
SICI code
0009-2673(199812)71:12<2903:GACARO>2.0.ZU;2-V
Abstract
The treatment of tribromofluoromethane with BuLi in THF-Et2O (2: 1) at -130 degrees 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 stereosel ectively to (E)-1-bromo- 1,2-difluoro olefin 5 via fluorination with Et2NSF 3, followed by dehydrobromination with lithium 2,2,6,6-tetramethylpiperidid e, while (E)-1-bromo-1-fluoro olefin was obtained with high selectivity by acetylation of 3, followed by reductive elimination using EtMgBr/(i-Pr)(2)N H. Difluoro olefin 5 underwent a cross-coupling reaction with an aryl, alke nyl, or alkynylmetal reagent to afford the corresponding fluoro olefin with retention of configuration. On the other hand, the treatment of RCH[OCH2O( CH2)(2)OCH3]CFBr2 with BuLi at -130 degrees C in the presence of 4-heptanon e gave the corresponding adduct diastereoselectively. The stereochemical ou tcome is explained in terms of chelation between lithium and oxygen atoms o f the (2-methoxyethoxy)methyl group. Starting with 2-phenylpropanal, a prod uct is obtained highly selectively containing three contiguous stereocenter s including a -CFBr- moiety.