Regiochemistry of Palladium(II)-assisted oxidative lactonisation reactions.

Annby, Ulf; Stenkula, M.; Andersson, Carina

doi:10.1016/s0040-4039(00)61381-3

Cited by 18 publications

(7 citation statements)

References 14 publications

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“…We speculated that the basic conditions might have been detrimental to the catalytic activity of Pd(II) through the formation of insoluble Pd(OH) 2 . Indeed, a free carboxylic acid and a weak base (NaOAc) were used in Larock's original procedure for the Pd lactonization 16c…”

Section: Resultsmentioning

confidence: 99%

“…By contrast, the mechanism of the Pd(II)-catalyzed lactonization reaction is still a subject of debate . In strict analogy to the allylic oxidation, two different pathways have been proposed: either an intramolecular acyloxypalladiation or a π-allyl intermediate formation through the allylic C−H bond activation . On the basis of this assumption, we anticipated that the C−H allylic activation would have converted both olefins 4 and 5 to the same π-allyl intermediate, which in turn accomplished the target compound after intramolecular carboxylate attack in an atom economical fashion (Scheme ).…”

Section: Introductionmentioning

confidence: 99%

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1,2-Oxopalladation versus π-Allyl Palladium Route. A Regioconvergent Approach to a Key Intermediate for Cyclopentanoids Synthesis. New Insights into the Pd(II)-Catalyzed Lactonization Reaction

et al. 2002

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Regioconvergent synthesis of the key lactone 1 from an equimolar mixture of the two olefins 4 and 5 was achieved by unique Pd(II) chemistry. The synthetic versatility of lactone 1 has been demonstrated in the synthesis of iridoids and of the endo-Corey lactone 2, which is a key intermediate for the F(2)-isoprostane synthesis. Upon exposure of the sodium salts of 4 and 5 to a catalytic amount of Pd(OAc)(2) under oxygen, in the presence of AcOH, an isomeric lactone 12 was obtained in addition to the title compound 1. The Pd(II) lactonization was optimized by fine-tuning all the factors participating in the catalytic cycle: solvent, oxidant, co-oxidant, and Pd(II) source. The Hosokawa's heterobimetallic couple emerged as the catalyst of choice. With a Cu(II)-Pd(II) couple, the redox process was transferred to copper, and the formal oxidation state of palladium remained constant during the reaction. By virtue of this new methodology, lactone 1 was obtained in a rewarding 60% yield, along with isomeric lactone 12 in 30% yield. A detailed mechanistic study was carried out in order to elucidate the formation of lactones 1 and 12. Lactone 1 was formed from either olefin 8 or olefin 10; on the other hand, lactone 12 was formed exclusively from olefin 10. An intramolecular 1,2-acyloxypalladiation was invoked for the transformation of 8 into 1, whereas the pi-allyl complexes 13 and 11 were involved in the transformation of olefin 10 into 12 and 1, respectively.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

1,2-Oxopalladation versus π-Allyl Palladium Route. A Regioconvergent Approach to a Key Intermediate for Cyclopentanoids Synthesis. New Insights into the Pd(II)-Catalyzed Lactonization Reaction

et al. 2002

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“…Commercially available 3-butyn-1-ol was protected as the silyl ether and converted to iodide 42 in high yield. Lactone 43 was prepared according to the published procedure and alkylated with iodide 42 to give a 4:1 mixture of diastereomers. The lactone was reduced to the hemiacetal and treated with the Wittig reagent.…”

Section: Resultsmentioning

confidence: 99%

Sequential Cyclization/Silylation of Dienynes Catalyzed by an Organoyttrium Complex

Molander

Retsch

1998

J. Org. Chem.

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The organoyttrium complex Cp*2YCH3·THF (Cp* = C5Me5) has been shown to be an effective precatalyst for the selective sequential cyclization/silylation of dienynes. The catalyst's ability to insert the alkyne in preference to the alkenes in a regioselective manner, combined with the high diastereoselectivity of the intramolecular insertion process, leads to bicyclo[3.3.0]octane products in high yield. The stereochemistry of the exocyclic olefin, the ring fusion, and the ring substituents are all controlled in the reaction. The cyclization of dienynes thus affords silylated carbobicyclics with high diastereoselectivities in excellent yields.

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“…The intramolecular oxidative acyloxypalladation of alkenoic acids affords lactones by either exo-or endo-cyclization, depending on the position of the double bond. 16 Intramolecular reaction of o-allylbenzoic acid with either stoichiometric amounts of PdCl 2 (CH 3 CN) 2 and Na 2 CO 3 or under the redox system PdCl 2 (CH 3 CN) 2 (2 mol %)/Cu(OAc) 2 ·H 2 O/O 2 and Na 2 CO 3 affords 3-methylisocoumarin (eq 10). 17 However, the same cyclization reaction in the presence of a catalytic amount of Pd(OAc) 2 under 1 atm of O 2 in DMSO leads to a (Z)-phthalide (eq 10).…”

Section: Palladium(ii)-catalyzed/promoted Addition Of Nucleophiles Acmentioning

confidence: 99%

Dichloro Bis(acetonitrile) Palladium

Carretero

Arrayás

2008

Encyclopedia of Reagents for Organic Synthesis

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Regiochemistry of Palladium(II)-assisted oxidative lactonisation reactions.

Cited by 18 publications

References 14 publications

1,2-Oxopalladation versus π-Allyl Palladium Route. A Regioconvergent Approach to a Key Intermediate for Cyclopentanoids Synthesis. New Insights into the Pd(II)-Catalyzed Lactonization Reaction

1,2-Oxopalladation versus π-Allyl Palladium Route. A Regioconvergent Approach to a Key Intermediate for Cyclopentanoids Synthesis. New Insights into the Pd(II)-Catalyzed Lactonization Reaction

Sequential Cyclization/Silylation of Dienynes Catalyzed by an Organoyttrium Complex

Dichloro Bis(acetonitrile) Palladium

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