Palladium catalyzed transformations of monoterpenes: stereoselective deuteriation and oxidative dimerization of camphene

Silva, Márcio José da; Gonçalves, José Aı́lton; Alves, Rosemeire Brondi; Howarth, Oliver W.; Gusevskaya, Elena V.

doi:10.1016/j.jorganchem.2003.10.016

Cited by 47 publications

(8 citation statements)

References 23 publications

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“…Despite the synthetic utility of expanding this reactivity toward non-conjugated alkenes, reports of such a transformation are rare. Notably, the Gusevskaya group developed a camphene dimerization reaction 11 and Loh and coworkers employed an alcohol or silyl ether directing group to achieve C(alkenyl)–H activation of 1,1-disubstituted non-conjugated terminal alkenes. 12 During the preparation of this manuscript, Chou and co-workers reported a carboxylate-directed C(alkenyl)–H alkenylation of 1,4-cyclohexadiene compounds, which undergo decarboxylative rearomatization in situ.…”

Section: Introductionmentioning

confidence: 99%

C(alkenyl)–H Activation via Six-Membered Palladacycles: Catalytic 1,3-Diene Synthesis

et al. 2018

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A catalytic method to prepare highly substituted 1,3-dienes from two different alkenes is described using a directed, palladium(II)-mediated C(alkenyl)-H activation strategy. The transformation exhibits broad scope across three synthetically useful substrate classes masked with suitable bidentate auxiliaries (4-pentenoic acids, allylic alcohols, and bishomoallylic amines) and tolerates internal nonconjugated alkenes, which have traditionally been a challenging class of substrates in this type of chemistry. Catalytic turnover is enabled by either MnO as the stoichiometric oxidant or co-catalytic Co(OAc) and O (1 atm). Experimental and computational studies were performed to elucidate the preference for C(alkenyl)-H activation over other potential pathways. As part of this effort, a structurally unique alkenylpalladium(II) dimer was isolated and characterized.

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Section: Introductionmentioning

confidence: 99%

C(alkenyl)–H Activation via Six-Membered Palladacycles: Catalytic 1,3-Diene Synthesis

et al. 2018

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“…− For several years, we have been interested in catalytic reactions of natural products aiming to add value to these low-cost raw materials. In particular, we have intensively studied cobalt- − and palladium-catalyzed− oxidations of monoterpenes. The most abundant nonfunctionalized substrates, such as limonene, pinenes, camphene, and myrcene, have been mainly used in our previous works.…”

Section: Introductionmentioning

confidence: 99%

Aerobic Palladium(II)/Copper(II)-Catalyzed Oxidation of Olefins under Chloride-Free Nonacidic Conditions

et al. 2009

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A chloride-free Pd(OAc)2/Cu(OAc)2 system catalyzes the oxidation of organic substrates by molecular oxygen in nonacidic methanol solutions. Terminal olefins, i.e., 1-hexene, 1-octene, styrene, and 2-vinylnaphthalene, give the corresponding methyl ketones without a significant double-bond isomerization of long-chain substrates. The catalyst also promotes an unusual allylic oxidation of sterically encumbered trisubstituted internal double bonds in acyclic polyenes able to form η2−η2-chelates with palladium. Linalool and nerolidol, mono- and sesquiterpenic allylic alcohols, give corresponding allylic ethers arising from the exclusive oxidation of the internal double bonds. Monosubstituted terminal double bonds in both substrates remain intact due to the deactivating effect of the allylic hydroxyl group. Dihydromyrcene, a nonfunctionalized monoterpenic diene, gives allylic ether and methyl ketone arising from the oxidation of both trisubstituted and terminal double bonds, respectively. On the other hand, internal double bonds in the substrates without a terminal olefinic bond, such as citronellol, citronellal, nerol, and citral, do not undergo oxidation under similar conditions. A steric possibility for chelation of the terminal and internal double bonds on the same palladium atom seems to be a crucial factor to determine the reactivity of the internal double bonds in these substrates toward oxidation. The presence of the second η2-coordinated double bond in these chelates favors the activation of the allylic C−H bond of the olefin, which results in η3-allyl intermediates and, then, in allylic ethers. Nerol, a primary allylic alcohol, is oxidized to (Z)-citral, although the process is complicated by further nonselective transformations of citral. All oxygenated terpenic derivatives obtained in the present work have a pleasant scent with a flower or fruit tinge and are potentially useful as components of synthetic perfumes.

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“…Previous study via NMR spectroscopy revealed that the palladium-catalysed camphene deuteriation reaction involves intermediates r-vinylcamphene-palladium [31]. This fact in addition to commonly reactions promoted by palladium, allows suggesting a possible pathway of formation of aldehyde camphene [32].…”

Section: Pdcl 2 -Catalysed Camphene Oxidation: a Brief Discussionmentioning

confidence: 91%

Palladium-Catalysed Oxidation of Bicycle Monoterpenes by Hydrogen Peroxide in Acetonitrile Solutions: A Metal Reoxidant-Free and Environmentally Benign Oxidative Process

Oliveira

Silva

2009

Catal Lett

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Currently, the oxidative transformations of natural olefins are complicated for competitive reactions such as isomerization, skeletal rearrangements and nucleophilic addition. These concurrent reactions are promoted by metal reoxidant, normally a Lewis acid, and by protic solvent. In this article, the oxidation of terpenes, namely camphene, b-pinene, a-pinene and 3-carene were performed in PdCl 2 /H 2 O 2 /CH 3 CN system. This metal reoxidant-free system showed highly efficient, especially on camphene and b-pinene oxidation, which resulted in the selective conversion of these substrates into epoxy-derivates and allylic oxidation products, respectively. Additionally, the effects of the principal reactional parameters such as the peroxide/catalyst and substrate/catalyst molar ratio were also investigated.

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Palladium catalyzed transformations of monoterpenes: stereoselective deuteriation and oxidative dimerization of camphene

Cited by 47 publications

References 23 publications

C(alkenyl)–H Activation via Six-Membered Palladacycles: Catalytic 1,3-Diene Synthesis

C(alkenyl)–H Activation via Six-Membered Palladacycles: Catalytic 1,3-Diene Synthesis

Aerobic Palladium(II)/Copper(II)-Catalyzed Oxidation of Olefins under Chloride-Free Nonacidic Conditions

Palladium-Catalysed Oxidation of Bicycle Monoterpenes by Hydrogen Peroxide in Acetonitrile Solutions: A Metal Reoxidant-Free and Environmentally Benign Oxidative Process

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