Dérivés de sucres à groupement gem‐dihalogénoéthényle

Abstract

Carbohydrate Derivatives Bearing a gem‐Dihalogenoethenyl Group Treated with the appropriate Wittig reagent, aldehydosugar derivatives (1–13) led in good to excellent yields to the expected gem‐difluoro, gem‐chlorofluoro‐and/or gem‐dichloroenoses (14–29). Examples of their dibromo analogues had been previously described (see e.g. [1]) but the diiodo derivatives could not be isolated, The influence of the conditions on the yields is reported as well as spectroscopic properties (particularly the long‐range 13C, 19F‐ and 1H, 19F‐coupling constants) of these new enoses.

Fluorinated Ylides and Related Compounds

“…99 An NMR study suggested that the ylidic carbon in R 3 AsdCH 2 has a pseudotetrahedral geometry (sp 3 ), 176,177 whereas X-ray crystallography has demonstrated the ylidic carbon to be planar (sp 2 ) when it bears an acyl group (fluorinated or nonfluorinated). 164,172 There was no typical ketone carbonyl absorption in the IR spectrum of [(pentafluoropropionyl)benzoylmethylene]triphenylarsorane (73). It was suggested that the ylidic charge was delocalized over the neighboring carbonyl groups.…”