On the Mechanism of Palladium(0)‐Catalyzed Reactions of Allylic Substrates with Nucleophiles. Origin of the Loss of Stereospecificity

Bäckvall, Jan‐E.; Granberg, Kenneth L.; Heumann, Andréas

doi:10.1002/ijch.199100003

Cited by 59 publications

(14 citation statements)

References 25 publications

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“…Doyle and co-workers reported an alternative solution for Pd(0)-catalyzed allylic fluorination. 60 In a preliminary investigation, a cyclic palladium(II)allyl complex 61,62 formed from the corresponding allyl chloride 63 underwent fluorination with AgF, delivering the product in 49% yield (NMR yield) along with 4% yield of the undesired product of elimination. The subsequent successful development of a catalytic variant for this reaction offered the possibility to define a protocol for enantioselective fluorination.…”

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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“…ESI-MS of the reaction mixture in C 6 D 6 showed series of signals consistent with elemental composition of cyclohexadiene oligomers, {C 6 H 8 } n (H,OH) + , n = 5-11. 4.14. cis/trans-Methyl 5-fluorocyclohex-3-ene-1-carboxylate (13) Under N 2 , a 26 mL PFA tube was charged with AgF (436 mg, 3.47 mmol), P(o-Tolyl) 3 (35 mg, 0.12 mmol), C 6 H 6 (6 mL) and trans-methyl 5-chlorocyclohex-3-ene-1-carboxylate [29] (202 mg, 1.16 mmol). The mixture was sonicated at +20 8C in the dark for 44 h, at which time complete conversion of the chloride was established by NMR of an aliquot.…”

Section: Preparative Scale Dehydrofluorination Ofmentioning

confidence: 99%

On the isolation of neat allylic fluorides

Lee

Yandulov

2009

Journal of Fluorine Chemistry

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“…Palladium‐catalyzed asymmetric allylic substitution may also depend on the leaving group attached to the allylic moieties 1d,5d,6…”

Section: Introductionmentioning

confidence: 99%

Effect of the Leaving Group on the Rate and Mechanism of the Palladium‐Catalyzed Isomerization of Cyclic Allylic Benzoates in Allylic Substitutions

et al. 2006

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In chloroform, the reaction of cis-5-phenylcyclohex-2-enyl 4-Z-benzoate (cis-1 Z , Z = NO 2 , Cl, H, Me, MeO) with Pd 0 complexes ligated to PPh 3 is reversible and proceeds with isomerization at the allylic position. The rate of isomerization of cis-1 Z to trans-1 Z depends on the catalytic precursor: Pd 0 (PPh 3 ) 4 Ͼ {Pd 0 (dba) 2 + 2PPh 3 } in agreement with an S N 2 mechanism in the rate-determining isomerization of the cationic (η 3 -allyl)palladium complexes formed in the oxidative addition. For a given precursor, the rate of isomerization of cis-1 Z to trans-1 Z also depends on the substituent Z, i.e., on the leaving group. The isomerization rate follows the same order as the leaving group properties:

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On the Mechanism of Palladium(0)‐Catalyzed Reactions of Allylic Substrates with Nucleophiles. Origin of the Loss of Stereospecificity

Cited by 59 publications

References 25 publications

Transition metal catalysis and nucleophilic fluorination

Transition metal catalysis and nucleophilic fluorination

On the isolation of neat allylic fluorides

Effect of the Leaving Group on the Rate and Mechanism of the Palladium‐Catalyzed Isomerization of Cyclic Allylic Benzoates in Allylic Substitutions

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