Synthesis of Fluorinated and Trifluoromethyl-Substituted Alkenes through the Modified Julia Olefination: An Update

Abstract

The modified Julia olefination is now a powerful tool for the synthesis of a large range of functionalized alkenes. This short review covers the last five years and provides an overview of the synthesis of mono-, difluoro-, and trifluoromethyl-substituted alkenes via the modified Julia olefination focusing on the novel scope of this reaction.1 Introduction2 Monofluoroalkenes2.1 Disubstituted α- and β-Monofluoroalkenes2.2 Bis(trifluoromethyl)phenyl Sulfones2.3 Conjugated Monofluoroalkenes2.4 Intramolecular Julia Olefination2.5 Smiles Rearrangement from Fluorinated Keto Sulfones2.6 Fluoroallylamines2.7 Fluorinated exo-Glycals2.8 Monofluoroalkenes with an α-Stereocenter at the Allylic Position3 1,1-Difluoroalkenes4 Trifluoromethyl-Substituted Alkenes5 Conclusion

Gold-Catalyzed Hydrofluorination of Internal Alkynes Using Aqueous HF

“…While these results indicate a limitation of the present system, i.e. a competitive hydration process, other successful approaches have been reported to prepare this class of compounds. ,,, …”

“…Herein, we report the successful development of a gold-catalyzed hydrofluorination of internal symmetrical and unsymmetrical alkynes using aqueous HF. Notably, this reaction uses one of the most economical sources of HF, is free of additional additives, avoids the use of halogenated solvents, and provides useful monofluoroalkenes as the final product …”

“…In both cases, the corresponding products ( 2u – v ) could be isolated as a single regio- and stereoisomer. These monofluoroalkenes are interesting, as they open the door to further functionalization by transformation of the carbon–halogen bond . When using ethyl phenylpropiolate as the substrate, the desired product 2w was isolated in low yield (34%) along with 50% of ethyl benzoylacetate, the hydration product.…”

Selective preparation of tetrasubstituted fluoroalkenes by fluorine-directed oxetane ring-opening reactions

“…However, the selective introduction of functional groups is not possible in these diols as the two hydroxy groups present similar chemical reactivity. Other approaches are available for a selective preparation of monofluoroalkenes including olefination or defluorination reactions or a sigmatropic rearrangement, but these approaches are limited and do not allow the synthesis of tetrasubstituted fluoroalkenes with good control of their geometry [ 18 – 21 ]. In order to develop a selective synthesis for tetrasubstituted fluoroalkenes we envisioned an alternative approach starting from fluoroalkylidene-oxetane derivatives and to the end we have studied the selectivity of the oxetane ring-opening reaction ( Fig.…”

Fluorination of Aryl-Alkenyl-Iodonium Salts for Preparing Alkenyl Fluorides

“…Numerous synthetic approaches have been developed to obtain selectively functionalized alkenyl fluorides which can be classified into five major categories based upon the organic reactions: (1) Horner-Wadsworth-Emmons, Horner-Wittig, Julia, Peterson, and Reformatskytype olefination reactions, (2) hydrofluorination of alkynes, (3) electronic fluorination of alkenyl metals, (4) reductive elimination reaction of multihalo compounds, and (5) various metal catalyzed cross-coupling reactions using fluoroalkenyl moiety containing synthons, etc. These synthetic methods have been summarized in several reviews and book chapters from different perspectives [1][2][3][7][8][9][10][11][12].…”