Synthesis of Conjugated Dienes and Polyenes

Mehta, Goverdhan; Rao, H. Surya Prakash

doi:10.1002/9780470682531.pat0105

Cited by 11 publications

(18 citation statements)

References 566 publications

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“…As a practical illustration the three well known examples in Scheme may be cited, with halide substituents as leaving groups in all cases. Whereas reductive elimination of 1,4‐dihalo‐2‐butenes 8 furnishes 1,3‐butadienes 9 ,1 change of the C 2 spacer to an acetylene moiety (1,4‐dihalo‐2‐butynes, 10 ) results in the formation of [3]cumulene 11 2…”

Section: Introductionmentioning

confidence: 99%

1,x‐Elimination Reactions: Extending the Limits of a Classical Organic Reaction

Werner

Hopf

Dix

et al. 2007

Chemistry A European J

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Alpha,omega-dibromo derivatives in which the two terminal carbon atom are separated by an unsaturated spacer unit ("pi spacer") undergo 1,x-elimination reactions (with x=6, 8, 10, and 14), using Mori's reagent (nBu3SnSiMe3/CsF). The resulting cumulenic intermediates cyclodimerize in a subsequent step yielding novel macrocyclic acetylenic and bridged aromatic compounds (cyclophanes). Thus 1,6-eliminations were carried out with dibromide 17 to yield 1,3,7,9-cyclododecatetrayne (20) and with benzylbromide 24 to provide cyclophanes 26 and 27. By 1,8-eliminations the 16-membered macrocycle 33 could be prepared from enediyne 31, the benzannelated 1,5-cyclooctadiyne 41 from dibromide 38, and a mixture of cyclophanes 45 and 46 from the precursor 43. 1,10-Eliminations were carried out successfully with dibromides 47, 50, and 53 yielding the corresponding unsaturated cyclophanes ("cyclophynes") 49, 52, and 55. The influence of the solvent on the cyclodimerization 47-->49 was investigated, with acetonitrile providing the highest yields. The heterophanes 59 a and b were obtained by 1,10-elimination of the precursor dibromides 57 a and b, and in an elimination experiment involving a 1:1 mixture of the dibromides 50 and 57 b the "mixed dimer" 60 was isolated, besides the homodimers 52 and 59 b. The method reached its limits with the 1,14-elimination of 68, 70, and 74 providing the cyclophanes 69, 71, and 75 in varying amounts. Two final debrominations with 76 and 77, which in principle could undergo 1,16- and 1,20-eliminations reactions, respectively, failed. The structures of the new cyclophanes 49, 50, 59 a, and 59 b were established by X-ray structural analysis; all other structure assignments rest on the usual spectroscopic and analytical data.

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Section: Introductionmentioning

confidence: 99%

1,x‐Elimination Reactions: Extending the Limits of a Classical Organic Reaction

Werner

Hopf

Dix

et al. 2007

Chemistry A European J

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“…The diene also occurs in many natural products with interesting biological activity. 1 A natural disconnection for the 1,3-diene motif is the formation of the central single bond. For linear and less-substituted branched dienes, Mizoroki-Heck, 2 ene-yne metathesis, 3 C-H vinylation, 4 and cross-coupling approaches 5 have been successful.…”

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confidence: 99%

“…For highly substituted and branched dienes with multiple rings, the most-used approach is cross-coupling of vinylmetal reagents with vinyl halides. 1,6 While these approaches have proven useful, relatively few highly substituted dienes have been synthesized and often require synthesis of an organometallic reagent.…”

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confidence: 99%

Multimetallic Ni- and Pd-Catalyzed Cross-Electrophile Coupling To Form Highly Substituted 1,3-Dienes

2018

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The synthesis of highly substituted 1,3-dienes from the coupling of vinyl bromides with vinyl triflates is reported for the first time. The coupling is catalyzed by a combination of (5,5'-bis(trifluoromethyl)-2,2'-bipyridine)NiBr and (1,3-bis(diphenylphosphino)propane)PdCl in the presence of a zinc reductant. This method affords tetra- and penta-substituted 1,3-dienes that would otherwise be difficult to access and tolerates electron-rich and -poor substituents, heterocycles, an aryl bromide, and a pinacol boronate ester. Mechanistically, the reaction appears to proceed by an unusual zinc-mediated transfer of a vinyl group between the nickel and palladium centers.

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“…Construction of linear conjugated π-systems presents unique synthetic challenges, because every CC bond has to be produced stereoselectively and with substituents introduced in a regioselective manner. In order to control the regio- and stereoselectivity, a number of catalytic cross-coupling methods have been developed that attach dienyl groups in a sequence of several steps, for example by a sequential appendage of two CC units (Scheme , part A). , A reaction that enables direct appendage of a C 4 unit will allow for a more convergent and efficient synthesis of conjugated dienes and polyenes. However, the development of this synthetic platform has been impeded by the lack of reactions that produce both CC bonds in a regio- and stereoselective manner, and the lack of dienylation reagents that are stable and readily available in a variety of substitution patterns.…”

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confidence: 99%

Highly Regio- and Stereoselective Catalytic Synthesis of Conjugated Dienes and Polyenes

et al. 2018

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Conjugated dienes and polyenes are typically synthesized by sequential introduction of C═C bonds. Here, we report a practical and scalable, catalytic dienylation that is highly regio- and stereoselective for both C═C bonds. The reaction is enabled by a stereoselective palladium-catalyzed cross-coupling that is preceded by a regioselective base-induced ring opening of readily available sulfolenes. The dienylation reaction is particularly useful for the synthesis of synthetically challenging dienes containing cis double bonds. We also show that the reaction can serve as a synthetic platform for the construction of conjugated polyenes.

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Synthesis of Conjugated Dienes and Polyenes

Abstract: Introduction Elimination Reactions Addition–Elimination Reactions Concerted Reactions W ittig and Related Reactions Coupling Reactions From Alkynes From Heterocyclic Compounds Miscellaneous … Show more

Cited by 11 publications

References 566 publications

1,x‐Elimination Reactions: Extending the Limits of a Classical Organic Reaction

1,x‐Elimination Reactions: Extending the Limits of a Classical Organic Reaction

Multimetallic Ni- and Pd-Catalyzed Cross-Electrophile Coupling To Form Highly Substituted 1,3-Dienes

Highly Regio- and Stereoselective Catalytic Synthesis of Conjugated Dienes and Polyenes

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