1,721,064 research outputs found
Palladium-catalyzed cyclocarbonilation of unsaturated alcohols and amines. Chemoselective synthesis of heterocycle-substituted γ- and δ-lactones and lactams.
No full textUnsaturated alcohols and amines react with carbon monoxide and
hydrogen, in the presence of a catalytic amount of palladium acetate and a phosphine ligand, to afford selectively heterocycle-substituted γ- and δ-lactones and lactams. The distribution of five- and six-membered ring compounds can be modulated by an appropriate combination of solvent and phosphine ligand. The
five-membered products are formed in two isomeric forms trans and cis with a modest diasteroselectivity (trans>cis)
Synthesis of new 3,5-diarylisoxazolidines by cycloaddition of oxaziridines and alkenes
No full textThis article reports a novel process of cycloaddition of C-aryloxaziridines with a variety of alkenes to afford stable, five-membered heterocycles 13–24. The steric hindrance of the tert-butyl group on the nitrogen atom of the oxaziridine is responsible for the high stereoselectivity of the cycloaddition reaction
ELECTRON-TRANSFER REACTIONS ON HINDERED OLEFINS INDUCED BY AMINIUM SALTS
No full textHindered olefins 1-6, by reaction with aluminum salts, can afford, in relation to the reaction conditions and the peculiar features of the reagents, different reaction products such as dioxetanes, epoxides, ketones, or homoallylic, allylic and vinylic halogenated derivatives
Stereoselective synthesis and functionalization of N-alkyl-beta-lactams
No full textNovel polyfunctionalized N-alkyl-beta-lactams were prepared with high stereoselectivity in an efficient manner by a palladium-catalyzed [2+2] carbonylative cycloaddition of allyl bromide with heteroarylidene N-alkyl-amines The type of alkyl group linked to the nitrogen atom influences the reaction stereoselectivity. Moreover, the C-3 and the C-4 positions of the azetidinone ring can be further stereoselectively functionalized inserting various groups through the generation of a stable azetidinyl carbanion and then captured by various electrophiles
Properties, Synthesis and Functionalizations of beta-Lactams
No full textA novel and efficient synthetic method for preparing in high stereoselectivity beta-lactams poly-functionalized is reported. A palladium-catalyzed [2+2] carbonylative cycloaddition of simple allyl halides and imines affords 2-azetidinones having alkyl or aryl substituents at the heterocyclic nitrogen atom, aryl or heteroaryl moiety linked at the C-4 carbon, and alkenyl groups beared to the C-3 carbon. Moreover, through the formation of a stable carbanion at the C-3 and the C-4, it is possible to further functionalize these latter positions with various electrophiles inserting, thus, more akyl groups or alcoholic and epoxidic functions in the azetidinone ring
“Sali di ammonoile: efficienti catalizzatori per processi di ossidazione indotti da preliminari processi monoelettronici”
No full textSynthesis of stable isoxazolines by [3+2] cycloaddition of oxaziridines with alkynes.
No full textN-Alkyl substituted oxaziridines undergo a [3+2] cycloaddition reaction with a variety of terminal alkynes to give the product isoxazolines, whose stability appears to depend on the electronic properties of the groups on the C-3 and C-5 positions. The presence of an electron withdrawing group on C-5 and/or
an electron donating group on C-3 causes isomerization of the isoxazolines to beta-amino enones
[3+2] Cycloaddition of Oxaziridines with Nitriles: Synthesis of 2,3-Dihydro-1,2,4-Oxadiazoles
No full textA new and simpler preparation of 2,3-dihydro-1,2,4-oxadiazoles by synchronus [3+2] cycloaddition between oxaziridines and nitriles is presented
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