Reactivity of 1-alkoxy π-allylpalladium complexes

Vicart, Nicolas; Cazes, Bernard; Goré, J.

doi:10.1016/0040-4039(94)02334-8

Cited by 37 publications

(16 citation statements)

References 15 publications

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“…The [Pd(PPh 3 ) 4 ]-catalyzed reaction of 25b with diethyl methylmalonate has been reported by Cazes and co-workers to yield only the branched product [16]. Consistent with Cazes results, the related phenoxy derivative 25a gave branched/linear ratios of b 20 : 1 in all cases ( Table 5).…”

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confidence: 77%

Highly Enantio- and Regioselective Allylic Alkylations Catalyzed by Chiral [Bis(dihydrooxazole)]molybdenum Complexes

Glorius

Neuburger

Pfaltz

2001

HCA

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In memory of Luigi M. VenanziA series of chiral C 2 -symmetric bis[dihydrooxazoles] with a trans-1,2-diaminocyclohexane backbone was synthesized. In view of the promising results obtained by Trost et al. with related bis[pyridine] ligands, we tested these new ligands in the enantioselective molybdenum-catalyzed allylic alkylation of 1-and 3-monosubstituted allylic substrates. Enantiomer excesses of up to 98% and branched/linear ratios of up to 11 : 1 were obtained with (E)-3-(alkyl)allyl carbonates. (E)-3-Phenoxyallyl acetate gave a branched/linear ratio of b 20 : 1 and an ee of 98%. Crystal structures of the free ligand 7a and of its tricarbonylmolybdenum(0) complex 28 are reported.Introduction. ± Transition-metal-catalyzed allylic substitution is one of the most efficient and most versatile methods for enantioselective CÀC and CÀheteroatom bond formation [1]. A number of chiral catalysts are available which afford high enantiomer excesses (ee) with many prochiral or racemic substrates. However, there are still classes of substrates which give unsatisfactory results with the known catalysts and, therefore, the search for new chiral ligands and catalyst systems continues.Unsymmetrically substituted allyl derivatives are particularly demanding substrates, because, in addition to the requirement of enantiocontrol, the problem of regioselectivity has to be addressed. With most Pd-catalysts, monosubstituted allyl systems such as 1-or 3-arylallyl derivatives react with C-nucleophiles preferentially at the unsubstituted terminus, giving rise to a linear, achiral product. It is only recently that catalysts have been discovered which allow the preparation of branched, chiral regioisomers from 1-or 3-arylallyl esters, with good enantio-and regioselectivity. Such a reversal of regioselectivity has been achieved by means of Pd complexes with certain chiral ligands such as 1 [2], W [3] and Ir [4] complexes derived from phosphinodihydrooxazoles 2, an Ir catalyst containing the phosphoramidite 3 [5] and, most recently, with a Mo complex [6] derived from the bis[pyridine] 4 [7]. In terms of regio-and enantioselectivity, the latter of these, developed by Trost et al. [6a,b], is the most selective catalyst available today, giving a branched/linear ratio of 49 : 1 and an ee of 99% in the reaction of methyl (E)-1-phenylallyl carbonate with dimethyl malonate.

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confidence: 77%

Highly Enantio- and Regioselective Allylic Alkylations Catalyzed by Chiral [Bis(dihydrooxazole)]molybdenum Complexes

Glorius

Neuburger

Pfaltz

2001

HCA

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“…The triple bond of alkyne 3 then nucleophilically attacks 5 to give vinyl cation 6 . We attribute the absolute regioselectivity of this insertion to the β‐oxygen effect whereby the presence of the oxygen atom inhibits the development of cationic character two positions away 18. Hydride delivery should occur opposite the bulky tributylstannyl moiety in 6 , thus leading to vinylstannane ( Z )‐ 4 via 7 and regenerating the catalyst.…”

Section: Methodsmentioning

confidence: 99%

Studies on the Mechanism of B(C₆F₅)₃‐Catalyzed Hydrostannylation of Propargylic Alcohol Derivatives

Oderinde

Organ

2012

Angewandte Chemie

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Doppelter H‐Verlust: Die Lewis‐Säure B(C6F5)3 katalysiert die regio‐ und stereoselektive Hydrostannylierung von Propargylalkoholen (siehe Schema). Zunächst abstrahiert sie ein Hydrid vom Stannan unter Bildung eines Borhydrid/Stannylkation‐Paars, dessen Stabilität von Solvens und Liganden abhängt. Deuteriummarkierung zeigt, dass das Alkenylkation sein Hydrid im nächsten Schritt nicht vom Borhydrid, sondern von einem zweiten Stannanmolekül erhält.

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“…These types of complexes are reaction intermediates in important palladium-catalyzed allylic substitution reactions [30][31][32][33][34], in which the regioselectivity of the reaction is controlled by the electronic effects of the acyloxy substituent. Interestingly, the nucleophilic attack on a-acyloxy (g 3 -allyl)palladium intermediates usually takes place at the acyloxy substituted carbon to give the branched allylic product [30][31][32][33], while the regioselectivity of the catalytic transformations via b-acyloxy (g 3 -allyl)palladium intermediates is reversed to give the linear allylic product [14,28,[35][36][37][38]. Although, several studies have appeared on the b-substituent effects in (g 3 -allyl)palladium complexes, the a-substituent effects received somewhat less attention.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and structural features of α-acyloxy-(η3-allyl)palladium complexes

Kjellgren

Kritikos

Szabó

2006

Journal of Organometallic Chemistry

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Reactivity of 1-alkoxy π-allylpalladium complexes

Cited by 37 publications

References 15 publications

Highly Enantio- and Regioselective Allylic Alkylations Catalyzed by Chiral [Bis(dihydrooxazole)]molybdenum Complexes

Highly Enantio- and Regioselective Allylic Alkylations Catalyzed by Chiral [Bis(dihydrooxazole)]molybdenum Complexes

Studies on the Mechanism of B(C₆F₅)₃‐Catalyzed Hydrostannylation of Propargylic Alcohol Derivatives

Synthesis and structural features of α-acyloxy-(η3-allyl)palladium complexes

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Reactivity of 1-alkoxy π-allylpalladium complexes

Cited by 37 publications

References 15 publications

Highly Enantio- and Regioselective Allylic Alkylations Catalyzed by Chiral [Bis(dihydrooxazole)]molybdenum Complexes

Highly Enantio- and Regioselective Allylic Alkylations Catalyzed by Chiral [Bis(dihydrooxazole)]molybdenum Complexes

Studies on the Mechanism of B(C6F5)3‐Catalyzed Hydrostannylation of Propargylic Alcohol Derivatives

Synthesis and structural features of α-acyloxy-(η3-allyl)palladium complexes

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Studies on the Mechanism of B(C₆F₅)₃‐Catalyzed Hydrostannylation of Propargylic Alcohol Derivatives