Captodative Substitution Effect in [2+2] Cycloadditions Between Allenes and Olefins

Coppe-Motte, Geneviève; Borghese, A.; Janousek, Z.; Merényi, R.; Viehe, H. G.

doi:10.1007/978-94-009-4758-0_32

Cited by 5 publications

(2 citation statements)

References 3 publications

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“…For example, 116 reacts with allene to give 117 upon heating at 140°C for two days [62]. Captodative allenes can even react at room temperature with captodative olefins; as an illustration, a-methoxycyanoallene 118 adds to 116 to form 119 in 41% yield [62]. Captodative dienes, such as the 2-cyano-l-aza-l,3-butadienes 128 and 129, also undergo hetero Diels-Alder reactions, both inter-and intramolecularly (Scheme 23).…”

Section: [2+2] Cycloadditionmentioning

confidence: 99%

Synthetic Utility of the Captodative Effect

Stella¹,

Harvey²

2001

Radicals in Organic Synthesis

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Section: [2+2] Cycloadditionmentioning

confidence: 99%

Synthetic Utility of the Captodative Effect

Stella¹,

Harvey²

2001

Radicals in Organic Synthesis

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“…In cross-cycloadditions captodative olefins easily give cyclobutanes when heated with fluoroolefins [t41]. They also react with aUenes to give methylenecyclobutanes [142], and with methylenecyclopropane to give spiro [2.3]hexanes [143].…”

Section: Application Of the Bond-forming Initiation Theory To The Spomentioning

confidence: 99%

Captodative olefins in polymer chemistry

Penelle

Padías

Hall

et al. 1992

Polymer Synthesis Oxidation Processes

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The radical polymerization behavior of captodative olefins such as acrylonitriles, acrylates, and acrylamides m-substituted by an electron-donating substituent is reviewed, including the initiated and spontaneous radical homo-and copolymerizations and the radical polymerizations in the presence of Lewis acids. The formation of low-molecular weight products under some experimental conditions is also reviewed. The reactivity of these olefins is analyzed in the context of the captodative theory. In spite of the unusual stabilization of the captodative radical, the reactivity pattern of these olefins in polymerization does not differ signifcantly from the pattern observed for other 1,1-disubstituted olefins. Classical explanations such as steric effects and aggregation of monomers are sufficient to rationalize the observations described in the literature. The spontaneous polymerization of acrylates e-substituted by an ether, a thioether, or an acylamido group can be rationalized by the Bond-Forming Initiation theory.

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Chemo‐, Regio‐, and Stereoselective Diels–Alder Reaction of Ambident Dienophilic Monothiomaleimide

et al. 1997

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Keywords: Cycloadditions / C = S Dienophile / N-Arylmonothiomaleimides / Chemo-, regio-, and stereoselectivity / AM 1 ~ calculation Both the C=S and C=C functionalities of N-arylmonothiomaleimides readily undergo a (4 + 21 cycloaddition reaction at ambient temperatures with both electron-donating and -withdrawing dienes. The C=S groups of N-arylmonothiomaleimides are generally more reactive than the C=C groups, especially toward dienes bearing conjugation and electronattracting groups, and provide mixtures of ortho,endo products 3 and orfho,exo products 4 with complete regioselectivity (100% orfho) and with high stereoselectivity (more than 86% endo). The C=C groups, on the other hand, display a high stereoselectivity (100% endo) but a low regioselectivity, providing ortho,endo adducts 5 and meta,endo adducts 6 in ratios ranging from 1: 1 to 6: 1. Compared with N-phenylmonothiomaleimide ( 1 ) , N-p-nitrophenylmonothiomaleimide ( l l a ) is more reactive and displays a higher C=S vs. C=C chemoselectivity in favor of C=S, while N-p-anisyl ( l l b ) and N-benzyl (1 lc) derivatives display quite the reverse reactivity and selectivity. N-Phenylmonothiocitraconimide (1 Id) serves as a C=S specific dienophile and reacts with dienes to furnish ortho,endo adducts 12 with excellent regio-and stereoselectivities (100% ortho,endo). Both hard (BF, . OEtz, TiC1,) and soft (CuBr . SMe2) Lewis acids enhance the reaction rate enormously and increase chemoselectivity in favor of C=S. The chemo-(C=S/C=C), regio-(ortholmeta) and stereochemical outcomes (endolexo) are rationalized by transition structure analysis based on AM1 calculation.Hetero Diels-Alder reactions of C=O121, C=Nl2I, and C=S[2p8] dienophiles and donor-substituted dienes are among the most powerful carbon-carbon and carbonheteroatom bond-forming processes and have long been of great interest to synthetic and theoretical organic chemists. In these reactions, C = O and C = N dienophiles react with donor-substituted unsymmetrical dienes to give [4 + 21 cycloadducts via path a (Scheme l), while C=S dienophiles activated by conjugation with electron-withdrawing groups (acyl, alkoxycarbonyl, CN, etc.) react selectively via path b[3g3h34c3g,5c1. Ordinary thioaldehydes and thioketones also serve as reactive dienophiles; however, they display a reverse regioselectivity, showing a preference for path a[3h3J,4d,bl. This contrasting regioselectivity of thiocarbonyl dienophiles has been addressed theoretically by Vedejs and H o~k [~l . Here, we report that (i) N-phenylmonothiomaleimide (1) serves as a very reactive ambident C=S and C = C dienophile toward variously substituted 1,3-butadienes (Scheme 2); (ii) the C=S group of 1 displays comparable reactivity to the C=C group of 1 toward donor-substituted dienes, while the C=S group is much more reactive than the C = C group towards dienes substituted with conjugating and electron-withdrawing groups; (iii) the C = S group reacts with most dienes with exclusive ortho regioselectivity and with excellent endo stereoselectivity (more t...

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Captodative Substitution Effect in [2+2] Cycloadditions Between Allenes and Olefins

Cited by 5 publications

References 3 publications

Synthetic Utility of the Captodative Effect

Synthetic Utility of the Captodative Effect

Captodative olefins in polymer chemistry

Chemo‐, Regio‐, and Stereoselective Diels–Alder Reaction of Ambident Dienophilic Monothiomaleimide

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