Palladium Catalyzed α-Addition of Certain Pronucleophiles to Alkoxyallenes

Yamamoto, Yoshinori; Al-Masum, Mohammed

doi:10.1055/s-1995-5148

Cited by 48 publications

(15 citation statements)

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“…[10] The choice of alkoxyl substituent in the allenic substrate 11 followed the precedent in the literature [15] and aimed at selecting the branched adduct (13 a) over the linear one (14). Decreasing the catalyst load [16] improved the ee, but left the regioselectivity unaltered (Table 1, entries 1,2).…”

Section: Resultsmentioning

confidence: 99%

Enantioselective Palladium‐Catalyzed Addition of 1,3‐Dicarbonyl Compounds to an Allene Derivative

Trost

Simas

Plietker

et al. 2005

Chemistry A European J

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Enhancing atom economy of the metal-catalyzed asymmetric allylic alkylation (AAA) shifts from the usual nucleophilic displacement of a leaving group to an addition of a pronucleophile to a double bond. Using 1-alkoxyallenes as proelectrophiles, the palladium-catalyzed AAA proceeds with 1,3-dicarbonyl compounds as pronucleophiles with excellent regioselectivity and enantiomeric excess under optimized conditions. The pH of the medium proved crucial for reactivity/selectivity. By using the more acidic Meldrum's acids, the reactions required a co-catalytic amount of Brønsted acid, such as trifluoroacetic acid. Single regioisomeric products of 82-99 % ee were obtained. On the other hand, the less acidic 1,3-diketones failed to react under such conditions. The fact that a less acidic acid like benzoic acid sufficed, suggested the need for general base catalysis as well. Thus, a mixture of triethylamine and benzoic acid proved optimal (ee's 93-99). Employment of the (R,R)-phenyl Trost ligand gave a product with S configuration. A model to rationalize the results has been developed.

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Section: Resultsmentioning

confidence: 99%

Enantioselective Palladium‐Catalyzed Addition of 1,3‐Dicarbonyl Compounds to an Allene Derivative

Trost

Simas

Plietker

et al. 2005

Chemistry A European J

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“…With these disappointing results in hand, we therefore turned our attention to other strategies involving the use of palladium catalysis. A palladium(II)‐mediated coupling of 1‐methoxy‐1,2‐propadiene with secondary alcohols for the synthesis of α,α′‐disubstituted dihydropyrans and tetrahydrooxepines has been accomplished by Rutjes et al9 This result along with others1c,10 comforted us in the choice of this strategy for realising this transformation. The results are summarised in Table 1.…”

Section: Resultsmentioning

confidence: 99%

Palladium‐Catalysed Isomerisation of 2‐Vinylidenehydrofurans to 1,3‐Dienes and Some Aspects of Their Reactivity

Ghobsi¹,

Hacini²,

Wavrin³

et al. 2008

Eur J Org Chem

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The transformation of easily accessible 2‐vinylidenehydrofurans into stable 1,3‐dienes has been achieved by using catalytic amounts of palladium(0). These valuable compounds were then engaged in subsequent Diels–Alder reactions giving access to complex heterocyclic cores found in numerous natural products. A rationale for the regioselectivity of the Diels–Alder reactions with vinylfurans has been provided by DFT calculations. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

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“…All types of nucleophiles including oxygen, nitrogen, carbon, sulfur or halogen compounds were used in such reactions. Usually alkoxy (aryloxy) allenes afford -adduct 138, aryl allenes bearing an electron-withdrawing group at the para-position affordadducts and mono-and dialkyl-substituted allens afford -adducts 140 [24].…”

Section: Reactions Of Allenesmentioning

confidence: 99%

“…All three possible regioisomers can be selectively produced by properly substituting the allene at its terminal. Alkoxy (aryloxy) allenes afford -adduct, arylallenes bearing an electron-withdrawing group at the para-position afford -adducts and mono-and dialkyl-substituted allens afford -adducts [24]. Palladium-catalyzed reactions of allenes with carbon and heteroatom nucleophiles leading to the formation of carbon-carbon and carbon-heteroatom bonds generally proceed with the involvement of a -allyl palladium intermediate, which plays an ever increasing role in organic synthesis [23b, 25].…”

Section: Introductionmentioning

confidence: 99%

Recent Progress in the Chemistry of Allenes

Hassan

2007

COS

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Allenes are important compounds in organic and synthetic organic chemistry and therefore a large number of studies on their synthesis and reactions have been reported so far. We report the most recent methods for the synthesis of allenes, including optically active forms and fluorinated and gem-difluorinated allenes, in this paper. Reactions such as nucleophilic addition of allenes were classified and discussed in details according to the nature of the nucleophile either oxygen, nitrogen, carbon or sulfur, whereas, inter-and intra-molecular cycloadditions reactions with a variety of unsaturated functionality were separately discussed. A collection of some useful reactions such as coupling reactions of allenes mediated by organometallic reagents, intramolecular cyclization of allenes with tethered amines, asymmetric dihydroxylation, and epoxidation of allenes are also included.

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Palladium Catalyzed α-Addition of Certain Pronucleophiles to Alkoxyallenes

Cited by 48 publications

References 0 publications

Enantioselective Palladium‐Catalyzed Addition of 1,3‐Dicarbonyl Compounds to an Allene Derivative

Enantioselective Palladium‐Catalyzed Addition of 1,3‐Dicarbonyl Compounds to an Allene Derivative

Palladium‐Catalysed Isomerisation of 2‐Vinylidenehydrofurans to 1,3‐Dienes and Some Aspects of Their Reactivity

Recent Progress in the Chemistry of Allenes

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