On the isolation of neat allylic fluorides

Lee, Eunsung; Yandulov, Dmitry V.

doi:10.1016/j.jfluchem.2009.02.012

Cited by 16 publications

(17 citation statements)

References 57 publications

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“…Nonetheless, the mildness of this reaction is demonstrated by the synthesis of cinnamyl fluoride in a >95% isolated yield, a compound known to be unstable on standing at room temperature. 59 This methodology was tolerant of sterically hindered substrates (mesityl groups) and those containing easily modified functional groups such as aryl bromide or benzylic chloride sub-motifs. For precursors that could lead to two regioisomeric products, only the linear allylic fluoride was formed with no detectable trace of branched allylic fluoride as determined by 19 F NMR of the crude reaction mixture prior to purification.…”

Section: Allylic Fluoridesmentioning

confidence: 99%

Transition metal catalysis and nucleophilic fluorination

2012

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Transition metal catalyzed transformations using fluorinating reagents have been developed extensively for the preparation of synthetically valuable fluorinated targets. This is a topic of critical importance to facilitate laboratory and industrial chemical synthesis of fluorine containing pharmaceuticals and agrochemicals. Translation to (18)F-radiochemistry is also emerging as a vibrant research field because functional imaging based on Positron Emission Tomography (PET) is increasingly used for both diagnosis and pharmaceutical development. This review summarizes how fluoride sources have been used for the catalytic nucleophilic fluorination of various substrates inclusive of aryl triflates, alkynes, allylic halides, allylic esters, allylic trichloroacetimidates, benzylic halides, tertiary alkyl halides and epoxides. Until recently, progress in this field of research has been slow in part because of the challenges associated with the dual reactivity profile of fluoride (nucleophile or base). Despite these difficulties, some remarkable breakthroughs have emerged. This includes the demonstration that Pd(0)/Pd(II)-catalyzed nucleophilic fluorination to access fluoroarenes from aryl triflates is feasible, and the first examples of Tsuji-Trost allylic alkylation with fluoride using either allyl chlorides or allyl precursors bearing O-leaving groups. More recently, allylic fluorides were also made accessible under iridium catalysis. Another reaction, which has been greatly improved based on careful mechanistic work, is the catalytic asymmetric hydrofluorination of meso epoxides. Notably, each individual transition metal catalyzed nucleophilic fluorination reported to date employs a different F-reagent, an observation indicating that this area of research will benefit from a larger pool of nucleophilic fluoride sources. In this context, a striking recent development is the successful design, synthesis and applications of a fluoride-derived electrophilic late stage fluorination reagent. This new class of reagents could greatly benefit preclinical and clinical PET imaging.

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Section: Allylic Fluoridesmentioning

confidence: 99%

Transition metal catalysis and nucleophilic fluorination

2012

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“…This result indicated that the conditions of allylic fluorination are sufficiently mild to prevent decomposition of 23, which is known to be unstable upon standing at room temperature. [13] The branched regioisomer 3-fluoro-3-phenylpropene that arises from fluorination at the benzylic position, and is easily differentiated by 19 F NMR spectroscopy, was not detected. This result contrasts with the fluorination of cinnamyl alcohol carried out using diethylaminosulfur trifluoride (DAST); a reaction that gives a mixture of regioisomers, with the branched product being formed predominantly (linear/branched 1:1.75).…”

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confidence: 98%

Palladium‐Catalyzed Allylic Fluorination

et al. 2011

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Mild and rapid: The title reaction is presented and its applicability to 18F radiolabeling is demonstrated (see scheme; TBAF=tetra‐n‐butylammonium fluoride, THF=tetrahydrofuran, dba=dibenzylideneacetone). The use of p‐nitrobenzoate as the leaving group is significant to the success of this catalytic organometallic fluorination process. A range of allylic fluorides were synthesized by this method.

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“…Because this by‐product was also formed in a blind experiment without toluene‐4‐trifluoromethanesulfonate, it was assumed to be an 18 F‐fluorination product of the cinnamyl ligand, which is eliminated from the Pd precatalyst during the generation of the active catalyst. A standard for the by‐product could not be synthesized because of the instability of allylic fluorides . With [(Cod)PdCl 2 ] as alternative Pd precatalyst, however, the by‐product was not observed in the subsequent syntheses.…”

Section: Resultsmentioning

confidence: 99%

Carrier‐effect on palladium‐catalyzed, nucleophilic ¹⁸F‐fluorination of aryl triflates

Cardinale

Neumaier

Kügler

et al. 2012

Labelled Comp Radiopharmac

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A recently published palladium‐catalyzed preparation of fluoroarenes starting from caesium fluoride attracted interest as a new alternative for radiofluorination. To test this method, a suitable protocol for the synthesis of 4‐[18F]fluorotoluene and 1‐[18F]fluoronaphthalene as model systems has been developed. The possibility to perform the reaction under no‐carrier‐added condition was of special interest. It was found out, however, that the reaction requires the presence of carrier, thus limiting the method to syntheses of radiotracers with low specific activity. Copyright © 2012 John Wiley & Sons, Ltd.

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On the isolation of neat allylic fluorides

Cited by 16 publications

References 57 publications

Transition metal catalysis and nucleophilic fluorination

Transition metal catalysis and nucleophilic fluorination

Palladium‐Catalyzed Allylic Fluorination

Carrier‐effect on palladium‐catalyzed, nucleophilic ¹⁸F‐fluorination of aryl triflates

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On the isolation of neat allylic fluorides

Cited by 16 publications

References 57 publications

Transition metal catalysis and nucleophilic fluorination

Transition metal catalysis and nucleophilic fluorination

Palladium‐Catalyzed Allylic Fluorination

Carrier‐effect on palladium‐catalyzed, nucleophilic 18F‐fluorination of aryl triflates

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Carrier‐effect on palladium‐catalyzed, nucleophilic ¹⁸F‐fluorination of aryl triflates