A key intermediate, difluoromethylene phosphobetaine, in the Wittig reaction of ClCF2CO2Na-Ph3P with aldehydes was synthesized and characterized, which confirmed the reaction mechanism. The decarboxylation of this stable intermediate was a convenient approach for Wittig difluroolefination. Its reactivity could be adjusted by the modification of the substituent on the phosphorus.

The interconversion between difluoromethylene ylide and difluorocarbene is described. The difluoromethylene ylide precursor, Ph3P(+)CF2CO2(-), could be turned into an efficient difluorocarbene reagent, whereas the classical difluorocarbene reagents, HCF2Cl and FSO2CF2CO2TMS, could generate highly reactive difluoromethylene ylide. Thus the Wittig difluoro-olefination and difluorocyclopropanation could be selectively realized by using the same reagent. In addition, the ylides obtained from different carbene sources showed different reactivity in Wittig reactions.

Difluoromethylation is astraightforwardand widely applied strategy used to incorporate HCF 2 into organic molecules.Incontrast, cyanation reagents are typically volatile or highly toxic,o rt hey require harsh reaction conditions. Incorporation of both CN and HCF 2 into organic molecules, such as alkenes,isaworthwhile but challenging task. Amethod for photocatalyzed cyanodifluoromethylationo fa lkenes has been developed, which employs aP h 3 P + CF 2 CO 2 À /NaNH 2 (or NH 3 )r eagent system. Ph 3 P + CF 2 CO 2 À functions as both the HCF 2 and CN carbon source.Acyanide anion is generated in situ under mild conditions,therebyavoiding the use of toxic cyanation reagents.The photocatalytic method permits cyanodifluoromethylation of ar ange of alkenes under mild room temperature conditions.T he CN group within the products may be further derivatized by standardmethods.