Fluorinative Rearrangements of Substituted Phenylallenes Mediated by (Difluoroiodo)toluene: Synthesis of α‐(Difluoromethyl)styrenes

Abstract

Phenylallenes undergo fluorinative rearrangement upon the action of (difluoroiodo)toluene in the presence of 20 mol % BF ⋅OEt to yield α-difluoromethyl styrenes. This unprecedented reaction was entirely chemoselective for the internal allene π bond, and showed remarkable regioselectivity during the fluorination event. Substituted phenylallenes, phenylallenes possessing both phenyl- and α-allenyl substituents, and diphenylallenes were investigated, and good functional-group compatibility was observed throughout. The ease with which allenes can be prepared on a large scale, and the operational simplicity of this reaction allowed us to rapidly access fluorine-containing building blocks that have not been accessed by conventional deoxyfluorination strategies.

Expanding organofluorine chemical space: the design of chiral fluorinated isosteres enabled by I(i)/I(iii) catalysis

“…Moreover, Murphy and co-workers have disclosed the geminal diuorination of phenylallenes using stoichiometric p-TolIF 2 via Lewis acid activation. 89 Catalysis-based platforms have been developed to complement these reagent-based approaches and include Kitamura and co-workers protocol to generate 2,2-diuoroethylarenes from simple styrenes using p-TolI as the catalyst with m-CPBA as the oxidant. 90 This laboratory has also reported the geminal diuorination of styrenes and extended it to include asubstituted styrenes bearing uorine-containing groups (Fig.…”

Reactions promoted by hypervalent iodine reagents and boron Lewis acids

“…In 2017, Murphy used phenylallene derivatives 57 for the synthesis of α-difluoromethyl styrene compounds 58 which can be employed as fluorinated building blocks. 64 Stoichiometric amounts of difluoro(p-tolyl)-λ 3 -iodane and BF 3 •OEt 2 were reacted with phenylallenes to afford the α-difluoromethyl styrenes 58. The reaction was found to be highly chemoselective with high functional group tolerance and proceeded via a fluorinative rearrangement mechanism.…”

Alkene Vicinal Difluorination: From Fluorine Gas to More Favoured Conditions

“…The 1,1-difluorination of alkenes via a phenonium ion had been previously studied, [50][51][52] most notably by Szabo 53 and then again by Jacobsen, 54 who employed a chiral iodoarene to transform styrenes into gem-1,1-difluorinated products with moderate to very good enantioselectivities and yields. Gilmour and co-workers applied their vicinal difluorination conditions to styrenyl substrates using the chiral catalyst 32 (Figure 12).…”