Enantiocontrol in Some Palladium- and Copper-Catalyzed Reactions.

Backvall, JE

doi:10.3891/acta.chem.scand.50-0661

Cited by 10 publications

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“…The very high regioselectivity, i.e., the exclusive nucleophilic attack at the distal position with respect to the bulky amino group, can be understood in terms of steric hindrance at the proximal position and is in line with Bäckvall observations. , The attack on the proximal position is rare and has only been reported either with nucleophiles other than β-dicarbonyls (e.g., Et 2 NH) 11,35 or when PhSO 2 was employed as the leaving group (rather than AcO) . While this manuscript was undergoing a referee review, another example has been published by Krafft, in which the regioslectivity of the nucleophilic attack on the η 3 -Pd-complex is controlled by the neighboring, small to medium size amino group .…”

Section: Resultssupporting

confidence: 71%

“…To examine the potential steering effect of a neighboring group on the formation of the η 3 -complex, we required 1,4-disubstituted olefins with one substituent serving as a leaving group (AcO) and the other capable of coordinating to the catalyst prior to the reaction. To this end, we prepared the cis -allylic acetates 8a and 8b (Scheme ), using the Bäckvall cis -chloroacetoxylation of 1,3-cyclohexadiene and 1,3-cycloheptadiene, respectively ( 6 → 7 ), , followed by the (Ph 3 P) 4 Pd-catalyzed replacement of the allylic chlorine with benzylamine ( 7 → 8 ) 2 …”

Section: Resultsmentioning

confidence: 99%

“…The syn -diastereoisomeric series could be analogously prepared from ( E , E )-hexa-2,4-diene. ,, However, this diene is no longer commercially available and would have to be synthesized, so, for practical reasons, we selected the less volatile ( E , E )-diene 18 (Scheme ) as the starting material. The latter diene was readily obtained from 1-hexyne via alumination with DIBAH (hexane, 40 °C, 16 h), followed by the CuCl-mediated dimerization in THF at room temperature for 4 h ( 16 → 17 → 18 ).…”

Section: Resultsmentioning

confidence: 99%

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The Stereochemical Dichotomy in Palladium(0)- and Nickel(0)-Catalyzed Allylic Substitution

and

Kočovský

1998

J. Am. Chem. Soc.

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The steric course of the first step of Pd(0)-catalyzed allylic substitution with stabilized C-nucleophiles can be completely reversed by a suitably positioned coordinating Ph2P group, resulting in an overall inversion (1 → 4 → 5), as opposed to the normally observed retention (1 → 2 → 3). Thus, on reaction with NaCH(CO2Me)2, the allylic acetate 10, containing a phosphinous amide moiety, gives 24 as a result of ret.−inv. pathway, whereas 9, lacking the coordinating group, affords the “normal” inv.−inv. product 23. The intermediate η3-complex 32, generated in the former reaction, has been characterized by 1H and 31P NMR spectroscopy. While this stereochemical control is highly successful with cyclic substrates, it does not operate in acyclic series, as documented by the reactivity of the anti-configured 1,4-functionalized hexenes 14 and 15, which both give the product of inv.−inv. pathway, i.e., 35 and 36, respectively. The syn-configured allylic substrates 21 and 22 exhibit the same pattern, irrespective of the presence of the coordinating neighboring group. The lack of overriding control in the latter instances has been attributed to a rotation about the C−C bond connecting the coordinating group to the allylic system, which allows the precoordinated Pd(0) to approach the allylic moiety from the face opposite to the leaving group (15 → 41 → 42). Precoordination of the catalyst to the Ph2P group is evidenced by substantial acceleration of the reaction in all cases studied. For the Ni(0)-catalyzed reaction of the allylic methoxy derivatives with MeMgBr, precoordination proved to be the prerequisite for the reaction to occur (50 → 51 → 52); ret.−ret. pathway was observed.

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Section: Resultssupporting

confidence: 71%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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The Stereochemical Dichotomy in Palladium(0)- and Nickel(0)-Catalyzed Allylic Substitution

and

Kočovský

1998

J. Am. Chem. Soc.

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“…In 1995, Bäckvall and van Koten reported the first example of a catalytic, enantioselective S N 2 0 substitution of a primary allylic acetate in the presence of a chiral copper complex [28,29].…”

Section: Catalytic Reactions With Chiral Ligandsmentioning

confidence: 99%

Copper‐Mediated Enantioselective Substitution Reactions

Karlström

Bäckvall

2002

Modern Organocopper Chemistry

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Novel tridentate diamino organomanganese(II) complexes as homogeneous catalysts in manganese(II)/copper(I) catalyzed carbon–carbon bond forming reactions

Donkervoort

Vicario

Jastrzebski

et al. 1998

Journal of Organometallic Chemistry

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The new, paramagnetic arylmanganese (II) (3a), n-Bu (3b)). Complex 2, using CuCl as a co-catalyst, is an effective catalyst system for cross-coupling of Grignard reagents with alkyl bromides and the 1,4-addition of organomagnesium halides to h,i-unsaturated ketones. No further additives or co-solvents are necessary. For both reactions a dramatic decrease in reaction times is observed when compared to standard manganese/copper systems. Alkyl bromides with unsaturated or heteroatom functionalities can be cross-coupled. Also, excellent reactivity towards normally unreactive i,i-disubstituted ketones has been observed in the 1,4-addition reaction.

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Enantiocontrol in Some Palladium- and Copper-Catalyzed Reactions.

Cited by 10 publications

References 0 publications

The Stereochemical Dichotomy in Palladium(0)- and Nickel(0)-Catalyzed Allylic Substitution

The Stereochemical Dichotomy in Palladium(0)- and Nickel(0)-Catalyzed Allylic Substitution

Copper‐Mediated Enantioselective Substitution Reactions

Novel tridentate diamino organomanganese(II) complexes as homogeneous catalysts in manganese(II)/copper(I) catalyzed carbon–carbon bond forming reactions

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