Five-Membered Ring Systems with O &amp; N Atoms

Cordero, Franca M.; Giomi, Donatella; Lascialfari, Luisa

doi:10.1016/b978-0-08-100017-5.00011-x

Cited by 4 publications

(1 citation statement)

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“…that would interfere with most of the reagents that were previously used in stoichiometric amounts. The above catalytic method has been referred to as the Machetti–De Sarlo reaction . The solvent dependence of the base catalytic effect has been noticed by other authors.…”

Section: Introductionmentioning

confidence: 87%

Competitive Copper Catalysis in the Condensation of Primary Nitro Compounds with Terminal Alkynes: Synthesis of Isoxazoles

et al. 2016

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Isoxazoles, mainly 3,5‐disubstituted, are prepared by catalytic condensation of primary nitro compounds with terminal acetylenes by using a copper/base catalytic system. The additional catalytic effect of the copper(II) salts is evidenced by comparing the kinetic profiles. Selectivity dependence on reaction conditions is considered for phenylacetylene in the following competitive processes: oxidative coupling of terminal alkynes to conjugated diynes catalyzed by CuII and base in the presence of air; production of furazans beside condensation with benzoylnitromethane to 3‐benzoylisoxazoles, as a result of the reaction of the dipolarophile with 3,4‐dibenzoylfuroxan; addition of electron‐poor alkynes (e.g., methyl propiolate) with themselves and with the nitro compound. Thus, oxidative coupling is negligible in reactions with “active” nitro compounds, whereas with nitroalkanes both products are observed: only trace amounts of isoxazoles are detected without copper. Similarly, in the presence of copper, 3‐benzoyl‐5‐phenylisoxazole is predominant over the furazan. Furthermore, condensations of electron‐poor alkynes give complex reaction mixtures in the presence of base alone, but cycloadducts are conveniently prepared with copper. The results indicate the practical and general utility of this catalytic method for synthetic practice.

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Section: Introductionmentioning

confidence: 87%