The asymmetric kharasch reaction. Catalytic enantioselective allylic acyloxylation of olefins with chiral copper(I) complexes and tert-butyl perbenzoate

Andrus, Merritt B.; Argade, Ankush B.; Chen, Xi; Pamment, Michael

doi:10.1016/0040-4039(95)00444-h

Cited by 164 publications

(72 citation statements)

References 23 publications

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“…[69] b-Aryl bromides can be obtained directly from anilines and activated olefins under the conditions discovered by Doyle. [83] As shown before, the protocol developed by Gorbovoi [69] for the functionalisation of nonactivated olefins such as 2-methallylchloride (38), is again critically dependent on the application of the arenediazonium ion as tetrafluoroborate salt.…”

Section: Nitrogenmentioning

confidence: 95%

“…In related reactions it has been shown that the presence of copper(II) ions strongly facilitates trapping of allyl radicals by a ligand transfer from copper to carbon within a copperA C H T U N G T R E N N U N G (III)-allyl complex F', followed by the reductive elimination of a copper(I) species. [38] Even weakly reactive anions such as acetates, trichloroacetates, Scheme 4. Reductive Meerwein arylation of vinylmethylketone [32] and methyl methacrylate.…”

Section: Hydrogenmentioning

confidence: 99%

“…[64] The capability of copper(II) ions to transfer ligands to allyl radicals via the formation of a copperA C H T U N G T R E N N U N G (III)-allyl intermediate has been proposed as mechanism for comparable reactions (Scheme 5). [38,65] While acetate ligands can be directly transferred to give the isomeric esters 36, the alcohols 33 are believed to evolve from the hydrolysis of previously formed sulfate esters. [64] An overview over reactions of aromatic diazonium salts with unsaturated compounds in the presence of oxygen and sulfur nucleophiles has been given by Grishchuk.…”

Section: Nitrogenmentioning

confidence: 99%

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Intermolecular Olefin Functionalisation Involving Aryl Radicals Generated from Arenediazonium Salts

Heinrich

2009

Chemistry A European J

280

104

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This minireview is aimed at giving an overview of recent advances in olefin functionalisation reactions involving aryl radicals generated from arenediazonium salts. Based on the well-known Meerwein arylation, in which an aryl and a halogen substituent are coupled to an olefinic substrate, new reaction types have been developed that allow the introduction of a broad spectrum of other atoms and functional groups at the place of the original halogen atom and that are applicable to an extended range of olefinic substrates.

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Section: Nitrogenmentioning

confidence: 95%

Section: Hydrogenmentioning

confidence: 99%

Section: Nitrogenmentioning

confidence: 99%

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Intermolecular Olefin Functionalisation Involving Aryl Radicals Generated from Arenediazonium Salts

Heinrich

2009

Chemistry A European J

280

104

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“…It was proposed that the reaction occurred via a radical mechanism, which was suggested to proceed in a concerted manner, with the copper center being intimately involved in the CÀO bond forming step through the allyl cuprate, 4 (Scheme 2 the reaction was performed in the presence of an aliphatic acid, the ester of this acid was obtained rather than the corresponding benzoate. In view of the potential utility of such a synthetic transformation, it does seem remarkable that the first synthetically useful asymmetric variant was only reported in the mid 1990s, independently by the groups of Pfaltz, [2] Andrus, [3] and Katsuki. [4] Pfaltz [2] and Andrus [3] and their co-workers both employed the same series of enantiomerically pure C 2 -symmetric bis(oxazoline) groups (5 a ± e) as the ligand in the presence of copper(i) triflate with cyclic olefinic substrates (Scheme 3).…”

Section: Catalytic Allylic Oxidation Of Alkenes Using An Asymmetricmentioning

confidence: 99%

Catalytic Allylic Oxidation of Alkenes Using an Asymmetric Kharasch–Sosnovsky Reaction

Eames

Watkinson

2001

Angew. Chem. Int. Ed.

230

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Kharasch and Sosnovsky reported the allylic oxidation of alkenes to give racemic allylic benzoates. This could be achieved efficiently using a tert‐butyl perester as the oxidant, in the presence of a copper or cobalt salt. The use of C2‐symmetric bis(oxazoline) ligands in the presence of copper(I) triflate with cyclic olefinic substrates gave the first synthetically useful asymmetric variant. The enantioselective control was good (up to 84 % ee) although yields were variable. In all cases the facial preference of the newly formed C−O bond was the same giving an S configuration at the allylic stereocenter. Lower stereocontrol was observed for large‐ring alkenes and substantially reduced enantioselectivities were found with open‐chain alkenes. This reaction has been further screened using a variety bis(oxazoline) and proline‐derived ligands, which give a direct correlation between the chirality of the ligand and the enantioselectivity obtained. Individual substrates were found to be extremely sensitive to both the ligand structure and copper salt used as well as the presence of additives such as zinc, hydrazine, and molecular sieves.

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“…Metal complexes with oxazoline ligands serve as catalysts for a variety of asymmetric transformations including cyclopropanation [1], aziridination [2], allylic displacement [3], imine additions [4], Diels-Alder [5] ,aldol [6],1,3-dipolar cycloaddition [7],reduction [8],and the ene reaction [9]. We and Pfaltz independently reported [10] that malonyl-derived bisoxazoline copper complexes of 1 and 2 (Scheme 1) give high selectivities (80%ee) in the Kharasch copper catalyzed allylic oxidation reaction [11], a significant improvement over earlier approaches [12]. As the utility of this class of ligands expands, efforts to improve reactivity and selectivity will depend on the availability of synthetic routes to modified bisoxazolines.…”

mentioning

confidence: 99%

Synthesis and preliminary use of naphthyl quinazoline and isoquinoline oxazolines for asymmetric allylic oxidation

Andrus

Sekhar

2001

Journal of Heterocyclic Chem

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This paper is dedicated to Professor Jerald S. Bradshaw, undergraduate mentor of MBA, with warmth and gratitude for his encouragement and outstanding leadership.Four new oxazoline ligands, 4-naphthyl-2-phenylquinazoline 4 and 1-naphthylisoquinoline 5 were made using Suzuki coupling, a Pictet-Gams reaction, and S-amino alcohol. Preliminary use as ligands for asymmetric copper catalyzed allylic oxidation with cyclohexene and perester showed promise providing S-cyclohexenyl benzoate product in moderate enantioselectivity (64%ee).J. Heterocyclic Chem., 38, 1265Chem., 38, (2001 [8],and the ene reaction [9]. We and Pfaltz independently reported [10] that malonyl-derived bisoxazoline copper complexes of 1 and 2 (Scheme 1) give high selectivities (80%ee) in the Kharasch copper catalyzed allylic oxidation reaction [11], a significant improvement over earlier approaches [12]. As the utility of this class of ligands expands, efforts to improve reactivity and selectivity will depend on the availability of synthetic routes to modified bisoxazolines. While the majority of bisoxazoline ligands remain methylene and pyridyl linked, recently biaryl bisoxazoline ligands have been reported and used as ligands in asymmetric reactions [13]. We synthesized and used the S,S,S -bis-toluyl bisoxazoline 3 as ligand for allylic oxidations and obtained products in the 70%ee range [14].In an effort to improve reactivity and selectivity, we now report the synthesis and preliminary use of two new novel ligands, 4-naphthyl-2-phenylquinazoline 4 and 1-naphthylisoquinoline 5 (Scheme 2). Brown and others have recently produced and investigated biaryl isoquinolinephosphines and indoles [15]. Quinazoline-phosphines have also been reported [16]. While oxazolines have been combined in ligands with sulfide and phosphine moieties, [17] oxazoline-quinazoline and isoquinoline dual-domain ligands have not been reported. The new oxazoline-quinazoline 4 was made using a Suzuki coupling and is obtained in conformationally stable S form. The biaryl oxazolineisoquinoline 5, made using a Pictet-Gams reaction, is not conformationally stable. Both were tested for use as ligands for asymmetric allylic oxidation.The synthesis of 4 began with the Suzuki coupling [18] of commercially available 4-chloro-2-phenylquinazoline 6 (AM-ex-OL) with 2-methyl-1-naphthylboronic acid [19] 7 under palladium catalysis to give the biaryl adduct 8 in 85% isolated yield (Scheme 3). Functionalization of the methyl group appended at the 2-position of the naphthyl moiety was performed using benzylic bromination. The dibromide 9 was formed using two equivalents of N-bromosuccinide under photolytic conditions in quantitative yield [20].The dibromide 9 was converted to the 2-naphthaldehyde 10 silver nitrate in 70% yield following the protocol of Walsh (Scheme 4) [20]. While many options are available at this point to effect the conversion to the carboxylic acid, only treatment with potassium permanganate in an acetone-water mixture resulted in formation of 11. Problems obtained with other ...

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The asymmetric kharasch reaction. Catalytic enantioselective allylic acyloxylation of olefins with chiral copper(I) complexes and tert-butyl perbenzoate

Cited by 164 publications

References 23 publications

Intermolecular Olefin Functionalisation Involving Aryl Radicals Generated from Arenediazonium Salts

Intermolecular Olefin Functionalisation Involving Aryl Radicals Generated from Arenediazonium Salts

Catalytic Allylic Oxidation of Alkenes Using an Asymmetric Kharasch–Sosnovsky Reaction

Synthesis and preliminary use of naphthyl quinazoline and isoquinoline oxazolines for asymmetric allylic oxidation

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