To What extent is a π-allylic intermediate involved in some palladium-catalyzed alkylations ?

Fiaud, Jean‐Claude; Malleron, Jean-Luc

doi:10.1016/s0040-4039(01)90332-6

Cited by 60 publications

(35 citation statements)

References 8 publications

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“…These results correlate well with previous findings, where chloride anions have a positive effect on enantiospecificity in Pd-catalyzed allylic alkylations. [4][5][6] For both precatalysts the enantiospecificity obtained using the preformed complexes was of the same order of magnitude as when the precatalysts were formed in situ (Table 2, cf. entries 1 and 11, and entries 12 and 15).…”

Section: A Reaction Catalyzed By the Symmetrical [(Hmentioning

confidence: 73%

“…The influence of the phosphine ligand was then investigated (Table 1, entries [3][4][5], and the presence of cyclohexyl moieties on the phosphine was found to be favourable (cf. Table 1, entries 2 and 3) while the very bulky alkylphosphine PA C H T U N G T R E N N U N G (t-Bu) 3 was detrimental to both enantiospecificity and reaction rate (Table 1, entry 5).…”

Section: A Reaction Catalyzed By the Symmetrical [(Hmentioning

confidence: 99%

“…[4][5][6] This phenomenon, which conflicts with the proposed reaction mechanism, has been dubbed the "memory effect", [2,3,5,6] and this may refer to both stereo-and regiospecificity.…”

Section: Introductionmentioning

confidence: 99%

“…The Tsuji-Trost reaction has been extensively studied and the mechanism has been investigated in detail. [2,3] However, in some cases a memory effect complicates the pattern of reactivity and this effect is not well understood, [4][5][6] although efforts have been made to study the mechanistic traits of memory effects. [7] The work presented here is an extension of an earlier study of the Tsuji-Trost reaction of a series of isomeric butenyl substrates, [5] and in the present investigation we have focused on enantiospecificity in the allylic alkylation of enantioenriched 2-cyclohexen-1-yl acetate.…”

Section: Introductionmentioning

confidence: 99%

“…[4,8,9] However, during the attack of Pd(0) the leaving group may be positioned either trans or cis to the ligand X, and the subsequent nucleophilic attack on the h 3 -allyl intermediate may also occur either trans or cis to X. Thus, for enantioenriched substrates, enantiospecificity (a memory effect) will be possible only if the h 3 -allyl intermediate is unsymmetric and if the catalyst shows some regiochemical preference in both formation and reaction of the intermediate (Figure 2).…”

Section: Introductionmentioning

confidence: 99%

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Memory Effects in Palladium‐Catalyzed Allylic Alkylations of 2‐Cyclohexen‐1‐yl Acetate

et al. 2007

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Section: A Reaction Catalyzed By the Symmetrical [(Hmentioning

confidence: 73%

Section: A Reaction Catalyzed By the Symmetrical [(Hmentioning

confidence: 99%

“…[4][5][6] This phenomenon, which conflicts with the proposed reaction mechanism, has been dubbed the "memory effect", [2,3,5,6] and this may refer to both stereo-and regiospecificity.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Memory Effects in Palladium‐Catalyzed Allylic Alkylations of 2‐Cyclohexen‐1‐yl Acetate

et al. 2007

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Palladium(0)-Catalyzed Isomerization of (Z)-1,4-Diacetoxy-2-butene − Dependence of η1- or η3-Allylpalladium as a Key Intermediate on the Solvent Polarity

Bouquillon

Мuzart

2001

Eur. J. Org. Chem.

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In the presence of Pd(PPh3)4, (Z)‐1,4‐diacetoxy‐2‐butene is selectively isomerized to (E)‐1,4‐diacetoxy‐2‐butene in THF while both (E)‐1,4‐diacetoxy‐2‐butene and 1,2‐diacetoxy‐3‐butene are obtained in DMF. Evidence to support the involvement of an η1‐allylpalladium in the former solvent and of a cationic η3‐allylpalladium in the latter as the keys intermediates is presented.

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Diastereoisomeric Cationic π-Allylpalladium-(P,C)-MAP and MOP Complexes and Their Relationship to Stereochemical Memory Effects in Allylic Alkylation

et al. 2000

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The axially chiral ligands 2-(diphenylphosphanyl)-2'-methoxy-1,1'-binaphthalene (MOP; 6) and 2'-dimethylamino-2-(diphenylphosphanyl)-1,1'-binaphthalene (MAP; 7) coordinate to a cationic allylpalladium fragment in an unusual bidentate (P,C)-mode through the triarylphosphane and ipso-carbon atom (C1'). The readily prepared MAP and MOP complexes [Pd[(P,C)-(L)](n3-allyl)][OTf] (9 (L = 7) and 10 (L = 6)) have been characterised in solution (NMR), in which two diastereoisomeric rotamers are observed. The stereochemical identity of the rotamers is established by one- and two-dimensional NMR spectroscopy experiments. In both the solid state and in solution, the allyl unit is shown to coordinate in a slightly distorted n3-mode that results in a more alkene-like character at the allyl terminus trans to phosphane ligand. The opposite allyl terminus, which is trans to the ipsocarbon atom (C1'), is more strongly bound and the dominant allyl stereodynamic process involves C-C bond rotation in an n'-allyl intermediate bound through this carbon. Palladium complexes of MAP and MOP are very efficient catalysts for allylic alkylation of racemic cyclopentenyl pivalate with [NaCH(CO2Me)2] in THF. Isotopic desymmetrisation revealed that the reaction occurs with powerful stereochemical memory effects and consequently with low global ee values. The memory effect is suggested to arise through selective generation of diastereoisomeric [Pd[(P,C)-L](n3-cyclopentenyl)]+ ions (L = MAP or MOP) and subsequent capture by nucleophile before ion-pair collapse or equilibration occurs.

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To What extent is a π-allylic intermediate involved in some palladium-catalyzed alkylations ?

Cited by 60 publications

References 8 publications

Memory Effects in Palladium‐Catalyzed Allylic Alkylations of 2‐Cyclohexen‐1‐yl Acetate

Memory Effects in Palladium‐Catalyzed Allylic Alkylations of 2‐Cyclohexen‐1‐yl Acetate

Palladium(0)-Catalyzed Isomerization of (Z)-1,4-Diacetoxy-2-butene − Dependence of η1- or η3-Allylpalladium as a Key Intermediate on the Solvent Polarity

Diastereoisomeric Cationic π-Allylpalladium-(P,C)-MAP and MOP Complexes and Their Relationship to Stereochemical Memory Effects in Allylic Alkylation

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