Synthesis and Heck Reactions of Ethenyl- and (Z)-Butadien-1-yl Nonaflate Obtained by the Fragmentation of Furan Derivatives

Lyapkalo, Ilya M.; Webel, M.; Reißig, Hans‐Ulrich

doi:10.1002/1099-0690(200111)2001:22<4189::aid-ejoc4189>3.0.co;2-i

Cited by 23 publications

(12 citation statements)

References 15 publications

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“…Rather the product from an apparent 1,2‐migration of the intermediate alkenyl palladium(II) species was obtained in good yield (79 %; Table 2, entry 1) 15. This result is in stark contrast to recent observations by Reissig and co‐workers, in which the Heck coupling between the corresponding vinyl nonaflate and methyl acrylate under phosphane‐free conditions was reported to give the expected coupling product 12c. Nevertheless, coupling of the same vinyl tosylate with a variety of alkenes revealed this isomerization to be quite effective with yields attaining 95 % and with exclusive trans selectivity in all but one case (Table 2, entries 2–6).…”

Section: Methodscontrasting

confidence: 65%

Heck Coupling with Nonactivated Alkenyl Tosylates and Phosphates: Examples of Effective 1,2‐Migrations of the Alkenyl Palladium(II) Intermediates

et al. 2006

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Considerable efforts have been undertaken by numerous groups in academia and industry over the past decade to expand the repertoire of coupling reagents in palladium(0)-catalyzed cross-coupling reactions.[1] In particular, alkenyl phosphates and tosylates have proven their worth in various cross-coupling reactions, such as the Stille, [2] Suzuki, [2e,f, 3] Negishi, [2b] Kumada, [2b, 3e, 4] Sonogashira, [2-b,e,f, 5] Buchwald-Hartwig, [4a, 6] carbonyl enolate, [3d] and Heck couplings, [7] as effective alternatives to the less stable and typically more expensive alkenyl triflates and nonaflates. [8] However, the majority of this work has focused on the use of activated vinyl phosphates and tosylates, such as a,b-unsaturated systems or a-heteroatom-substituted alkenes, for which the oxidative-addition step is nonproblematic with palladium(0) catalysts bearing aryl phosphine ligands. Less attention has been devoted to nonactivated counterparts, most likely because of the greater difficulty in carrying out the first step of the catalytic cycle, namely the oxidative addition. [3d, 4, 5, 9] We now report on catalyst systems composed of a palladium complex with a basic, hindered alkyl phosphine that can promote the Heck coupling of nonactivated vinyl tosylates and phosphates with electron-deficient alkenes in good yields, thereby increasing the scope of this important cross-coupling reaction. Furthermore, during these studies we observed an interesting 1,2-isomerization with certain alkenyl tosylates and phosphates under reaction conditions that provide coupling yields as high as 95 %. A mechanistic proposal supported by experimental results and DFT calculations is included.To identify suitable reaction conditions for Heck couplings with nonactivated alkenyl tosylates and phosphates, we examined the use of palladium complexes with the ever increasingly popular bulky electron-rich phosphines.[10] All tosylates and phosphates were prepared from starting ketones by base-promoted proton extraction and reaction with tosyl anhydride (Ts 2 O) or (PhO) 2 POCl, as earlier reported. [4b, 11, 12] Initial coupling attempts were performed between the tosylate 1 and ethyl acrylate (Scheme 1). After examining a variety of reaction conditions, we noted that a combination of [PdCl 2 (cod)] (cod = 1,5-cyclooctadiene; 5 mol %) and the P(tBu) 3 HBF 4 salt [13] (10 mol %) in the presence of dicyclohexylmethylamine (2 equiv) in dimethylformamide (DMF) at 85 8C could furnish the diene 2, albeit in low yield (approximately 5 %). The addition of one equivalent of LiCl, however, had a dramatic effect on the reaction outcome, thus providing a 50 % yield of the diene 2 after 24 hours. [14] Increasing the reaction temperature to 100 8C improved the coupling yield to 66 %. Other reactions conditions, including change of solvent or examination of alternative catalyst combinations, were incapable of promoting the cross-coupling.To probe the scope of these reaction conditions, we examined the Heck coupling of a variety of alkenyl tosylates ...

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Section: Methodscontrasting

confidence: 65%

Heck Coupling with Nonactivated Alkenyl Tosylates and Phosphates: Examples of Effective 1,2‐Migrations of the Alkenyl Palladium(II) Intermediates

et al. 2006

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“…It was observed that the coupling was influenced by the presence of lithium chloride as the co-catalyst, the product (3 E , 5 Z )-octa-3,5,7-trien-2-one ( 15 ) was obtained in good yields and high ( E )-selectivity. In fact as expected, nonaflate 14 seemed to react while retaining its configuration as illustrated in Scheme 8 [ 15 ].…”

Section: 13-dienessupporting

confidence: 64%

The Heck Reaction Applied to 1,3- and 1,2-Unsaturated Derivatives, a Way towards Molecular Complexity

et al. 2010

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This review is an overview of the last ten years’ use of the Mizoroki–Heck coupling applied to 1,2- and 1,3-dienes. Since both these systems form π-allyl palladium intermediates in Pd(0) coupling, they show particular chemical behavior. Many examples of 1,2-dienes Heck reactions are presented. 1,2-Dienes are important substrates because of their high reactivity that makes them useful building blocks for the synthesis of biologically relevant structures.

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“…The substrate was reacted with the alkyl acrylates 12a (R 1 = Me) and 12b (R 1 = t- Bu) under phosphine-free conditions [33–34] using 6 mol % of palladium(II) acetate, triethylamine as base and lithium chloride [35] leading to the expected coupling products syn - 13 and syn - 14 in 39% and 82% yield, respectively (Scheme 5). In both cases, only the E -configured 2-substituted alkyl acrylates were isolated.…”

Section: Resultsmentioning

confidence: 99%

Iodination of carbohydrate-derived 1,2-oxazines to enantiopure 5-iodo-3,6-dihydro-2H-1,2-oxazines and subsequent palladium-catalyzed cross-coupling reactions

Medvecký

Linder

Schefzig

et al. 2016

Beilstein J. Org. Chem.

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Iodination of carbohydrate-derived 3,6-dihydro-2H-1,2-oxazines of type 3 using iodine and pyridine in DMF furnished 5-iodo-substituted 1,2-oxazine derivatives 4 with high efficacy. The alkenyl iodide moiety of 1,2-oxazine derivatives syn-4 and anti-4 was subsequently exploited for the introduction of new functionalities at the C-5 position by applying palladium-catalyzed carbon–carbon bond-forming reactions such as Sonogashira, Heck, or Suzuki coupling reactions as well as a cyanation reaction. These cross-coupling reactions led to a series of 5-alkynyl-, 5-alkenyl-, 5-aryl- and 5-cyano-substituted 1,2-oxazine derivatives being of considerable interest for further synthetic elaborations. This was exemplarily demonstrated by the hydrogenation of syn-21 and anti-24 and by a click reaction of a 5-alkynyl-substituted precursor.

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Synthesis and Heck Reactions of Ethenyl- and (Z)-Butadien-1-yl Nonaflate Obtained by the Fragmentation of Furan Derivatives

Cited by 23 publications

References 15 publications

Heck Coupling with Nonactivated Alkenyl Tosylates and Phosphates: Examples of Effective 1,2‐Migrations of the Alkenyl Palladium(II) Intermediates

Heck Coupling with Nonactivated Alkenyl Tosylates and Phosphates: Examples of Effective 1,2‐Migrations of the Alkenyl Palladium(II) Intermediates

The Heck Reaction Applied to 1,3- and 1,2-Unsaturated Derivatives, a Way towards Molecular Complexity

Iodination of carbohydrate-derived 1,2-oxazines to enantiopure 5-iodo-3,6-dihydro-2H-1,2-oxazines and subsequent palladium-catalyzed cross-coupling reactions

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