Synthesis of Chiral Hypervalent Trifluoromethyl Organobismuth Complexes and Enantioselective Olefin Difluorocarbenation Screenings.

Two hypervalent trifluoromethyl organobismuth complexes were prepared from commercially available chiral amines, (R)-1-cyclohexylethylamine and (1R, 2R, 3R, 5S)-(-)-isopinocampheylamine; however, only the complex from the latter amine was prepared as a single stereoisomer. Both organobismuth complexes were fully characterized by NMR spectroscopy and single-crystal X-ray crystallography, revealing that the structures were similar to previously reported complexes with a hypervalent Bi-N bond. The complexes were catalytically active in olefin difluorocarbenation with Ruppert-Prakash reagent (TMS-CF3 ) used as a terminal source of CF2 . The catalyst derived from isopinocampheylamine was screened with three prochiral olefins of various reactivity in DCM and toluene. All reactions afforded the 1,1-difluorocyclopropanes in good yields, but no enantiomeric excess was observed.

Modified Julia Olefination on Anhydrides: Extension and Limitations. Application to the Synthesis of Maculalactone B.

The preparation of exo-enol esters from cyclic anhydrides is reported using a modified Julia olefination. The reaction is highly stereoselective. The Smiles rearrangement can be performed in a one-pot process, giving a straightforward access to exo-enol lactones. Furthermore, the reaction was extended to semistabilized sulfones, and this methodology was applied to the synthesis of maculalactone B.