Organotin nucleophiles. 6. Palladium-catalyzed allylic etherification with tin alkoxides

Keinan, Ehud; Sahai, Mahendra; Roth, Zeev; Nudelman, Abraham; Herzig, J.

doi:10.1021/jo00219a023

Cited by 91 publications

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“…Nevertheless, the Pd-catalyzed substitution reaction is not inhibited under these conditions. When 2 was added to the mixture, substitution was completed within 2.5 h, resulting in 3-phenoxy-l-phenylbut-l-ene (10) (eq 6). A situation very similar to that described in eq 6 was observed even in the case of 7 when TMSCl(2 equiv per Pd) was added to the reaction mixture; even after 24 h at room temperature no elimination was observed (eq 7).…”

Section: Keinan and Roth I Stereochem'cal Control In Pd-catalyzed Allmentioning

confidence: 64%

Stereochemical Control in Palladium‐catalyzed Allylic Etherification

Keinan

Roth

1990

Israel Journal of Chemistry

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Abstract. Two alternative approaches for increasing the stereospecificity of Pd(0)-catalyzed allylic etherification are presented, both of which also suppress product isomerization and elimination. One of them involves addition of chlorotrimethylsilane to a benzene reaction mixture. In the model reaction studied, it increases the ratio of the two stereoisomeric products, arising from either retention or inversion of configuration at the allylic carbon, from 3:l to 9:1, respectively. The second approach involves the employment of both donor-and acceptor-chelating ligands. Essentially 100% stereospecificity (retentionof configuration) was achieved when the reaction was carried out in benzene at 60 O C in the presence of Pd&dba), and bis-1,2-diphenylphosphinoethane.

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Section: Keinan and Roth I Stereochem'cal Control In Pd-catalyzed Allmentioning

confidence: 64%

Stereochemical Control in Palladium‐catalyzed Allylic Etherification

Keinan

Roth

1990

Israel Journal of Chemistry

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“…Enantioselective reactions of phenoxides are well documented, [7][8][9] but no metal catalyzes intermolecular enantioselective allylations of alkoxides with broad scope. [10][11][12][13] Lee and Kim [14] as well as Evans and Leahy [15] demonstrated that zinc and copper alkoxides were more reactive for allylic substitution with achiral palladium and rhodium catalysts than alkali metal alkoxides. The palladium-catalyzed reactions generated achiral ethers, but the rhodium-catalyzed reactions formed branched chiral ethers.…”

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confidence: 99%

Iridium‐Catalyzed Intermolecular Allylic Etherification with Aliphatic Alkoxides: Asymmetric Synthesis of Dihydropyrans and Dihydrofurans

2004

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Elimination and racemization limit the synthesis of sterically hindered ethers, [1] such as a-chiral ethers, by the Willamson synthesis. Enantioselective transition-metal-catalyzed allylic substitution [2][3][4][5][6] could be used to prepare these materials from achiral or racemic allylic electrophiles, but intermolecular enantioselective reactions of allylic acetates or carbonates with alkoxides are limited. Enantioselective reactions of phenoxides are well documented, [7][8][9] but no metal catalyzes intermolecular enantioselective allylations of alkoxides with broad scope. [10][11][12][13] Lee and Kim [14] as well as Evans and Leahy [15] demonstrated that zinc and copper alkoxides were more reactive for allylic substitution with achiral palladium and rhodium catalysts than alkali metal alkoxides. The palladium-catalyzed reactions generated achiral ethers, but the rhodium-catalyzed reactions formed branched chiral ethers. Reactions of primary alkoxides with optically active allylic acetates occurred with predominant retention of configuration, but reactions of secondary and tertiary alkoxides were conducted with racemic allylic electrophiles. Because the products from reactions of primary alkoxides can be formed by alkylation of an optically active alcohol, but products from reactions of secondary alkoxides cannot, a catalyst that forms optically active products from hindered alkoxides and allylic carbonates is synthetically valuable. We report herein enantioselective reactions of primary, secondary, and tertiary alkoxides with achiral allylic carbonates to form branched chiral allylic ethers in high yields and with high stereoselectivity in the presence of an iridium catalyst containing a phosphoramidite ligand (Scheme 1). [16][17][18][19][20][21][22] To optimize the conditions for the allylation of aliphatic alkoxides with iridium-phosphoramidite catalysts, we studied the reactions of cinnamyl carbonate with benzyloxides (Table 1). Careful selection of carbonate, alkoxide counterion, and nitrogen substituents in the ligand was essential for high yields. Cinnamyl carbonates with small alkyl groups underwent transesterification in competition with etherification, but tert-butyl cinnamyl carbonate (1 a) provided the

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“…The absolute stereochemistry is set in the first step and relies upon the ability of the catalyst to differentiate between the enantiotopic leaving groups in 49.F ortunately, L1 is extraordinarily well-suited for desymmetrizations of this type, and 51 was formed in excellent enantiopurity.D eoxygenation of this isoxazoline-2-oxide with SnCl 2 followed by furtherr eduction with Mo(CO) 6 afforded b-hydroxyester 52, whereas treating 51 with Mo(CO) 6 directly afforded the analogous syn-b-hydroxynitrile (not shown). The amide anion in the resultantspecies 64 cyclized onto the pendant p-allyl to generate ac yclic carbamate (65), which upon reduction and deprotection gave rise to 66. Allylic substitution of 53 with chloropurine 54 followed by basic hydrolysisa fforded carbovir (55), whereas as imilar sequence with adenine (56)a st he nucleophile led to aristeromycin (57).…”

Section: Scheme11 Semi-synthesis Of Glaucasterolmentioning

confidence: 99%

Annulative Allylic Alkylation Reactions between Dual Electrophiles and Dual Nucleophiles: Applications in Complex Molecule Synthesis

Trost

Kalnmals

2019

Chemistry A European J

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Metal-catalyzed allylic alkylation reactions between dual nucleophiles and dual electrophiles represent ap owerful set of methodsf or the synthesis of small-, medium-, and even large-sized rings. Using this strategy,ahandful of simple allylic diol derivatives can be transformed into a broad array of complexc arbo-and heterocycles of varying ring sizes in just as ingle step. Because of their ability to rapidly generate complexity, annulative allylic alkylationr eactions between dual nucleophiles and dual electrophiles have been extensively employed in the total synthesis of both naturalp roducts and pharmaceuticalcompounds.Scheme1.GeneralScheme for metal-catalyzed allylic alkylation.Scheme2.GeneralScheme for annulative allylic alkylation reactionsu sing a dual electrophile.Scheme3.Differenttypesofa nnulativeallylic alkylation reactions.Scheme4.GeneralScheme for allylic alkylation reactionsi nvolving 1,1-substitutions.

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Organotin nucleophiles. 6. Palladium-catalyzed allylic etherification with tin alkoxides

Cited by 91 publications

References 0 publications

Stereochemical Control in Palladium‐catalyzed Allylic Etherification

Stereochemical Control in Palladium‐catalyzed Allylic Etherification

Iridium‐Catalyzed Intermolecular Allylic Etherification with Aliphatic Alkoxides: Asymmetric Synthesis of Dihydropyrans and Dihydrofurans

Annulative Allylic Alkylation Reactions between Dual Electrophiles and Dual Nucleophiles: Applications in Complex Molecule Synthesis

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