Regiospecific synthesis of symmetrical (1E,3E) 2,3-difluoro-1,4-diphenyl-buta-1,3-dienes via palladium-catalyzed cross-coupling of (Z) 2-bromo-2-fluoroethenylbenzenes in presence of bis(pinacolato)diboron

Stereoselective Synthesis of Difluorinated 1,3-Dienes via Palladium-Catalyzed C-F Bond Activation of Tetrasubstituted gem-Difluoroalkenes

A highly diastereoselective Pd(0)-catalyzed synthesis of difluorinated 1,3-dienes is described. Symmetrical 1,3-dienes containing a vicinal difluoro moiety can be obtained as single diastereomers from tetrasubstituted gem-difluoroalkenes. The reaction presumably proceeds through a stereoselective twofold Pd-catalyzed Miyaura borylation/Suzuki-Miyaura cross-coupling of the C-F bond. Moreover, modular synthesis of unsymmetrical difluorinated 1,3-dienes is also achievable by the coupling between gem-difluoroalkenes and borylated monofluoroalkenes.

Concise preparation of fluorine-containing carbocycles involving the Diels–Alder reaction using fluorinated alkene or diene derivatives

The Diels–Alder reactions of trifluorovinyl substances with various dienes or 2,3-difluorobuta-1,3-dienes with various dienophiles proceeded well to give the corresponding trifluorinated cyclohexenes or vic-difluorocyclohexenes in acceptable yields, respectively.

Palladium-catalyzed stereoconvergent formylation of (E/Z)-β-bromo-β-fluorostyrenes: straightforward access to (Z)-α-fluorocinnamic aldehydes and (Z)-β-fluorocinnamic alcohols

We report here the stereoconvergent formylation of (E/Z)-β-bromo-β-fluorostyrene mixtures with carbon monoxide and sodium formate catalyzed by palladium. Optimization of reaction conditions leads to the corresponding pure (Z)-α-fluorocinnamaldehydes in good yields. The reaction was extended to styrenes bearing electro-attracting or electro-donating groups. The obtained α-fluoroaldehydes were smoothly reduced to the corresponding (Z)-β-fluorocinnamic alcohol by NaBH(4). The reaction could be performed on functionalized substrates as demonstrated by the access to the glucoside of β-fluoroconiferyl alcohol, (Z)-β-fluoroconiferin, a strong inhibitor of lignin polymerization.