Showing papers on "Pyrroline published in 2007"

Radical reactions of [60]fullerene mediated by manganese(III) acetate dihydrate.

Abstract: Mn(OAc)3 x 2H2O is an excellent reagent to promote free radical reactions of C60. C60 reacted with various methylene active compounds, methyl ketones, beta-enamino carbonyl compounds, carboxylic acid derivatives, and diallylamines in the presence of Mn(OAc)3 x 2H2O to afford singly-bonded fullerene dimers, 1,4-bisadducts and 1,16-bisadducts of C60, C60-fused dihydrofuran derivatives, methanofullerenes, C60-fused pyrroline derivatives, C60-fused lactone derivatives, and C60-fused pyrrolidine derivatives. Mn(OAc)3 x 2H2O was successfully employed to transform ArC60-H into ArC60-OAc.

Partial reduction of pyrroles: application to natural product synthesis

Abstract: The partial reduction of N-Boc pyrroles has been explored giving stereoselective routes to disubstituted pyrrolines in good yields and with excellent diastereoselectivities. A novel methodology has been developed to carry out reductive aldol reactions on 2-substituted N-Boc pyrroles; use of aldehydes under reductive aldol conditions gave the anti aldol product in good selectivity. This chemistry was used as the key transformation in a synthesis of omuralide, which was achieved in 13 steps and 14% overall yield. We also report a methodology for selectively forming either cis or trans 2,5-disubstituted pyrrolines via a partial reduction of an electron-deficient N-Boc pyrrole. The trans pyrroline formed using this route was utilized in the syntheses of the polyhydroxylated pyrrolizidine natural products hyacinthacine A1 and 1-epiaustraline. Further investigation has led to the development of routes to enantiopure substituted pyrroline compounds. This has been achieved via a chiral protonation approach using easily accessible chiral acids, such as ephedrine and oxazolidinones, to quench enolates formed during the partial reduction process. Alternatively, enzymatic desymmetrization of symmetrical diol compounds formed from the partial reduction products of substituted pyrroles is also reported. This leads to formation of both enantiomers of 2,2- and 2,5-disubstituted N-Boc pyrrolines in excellent ee and yields. © 2007 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 7: 180–190; 2007: Published online in Wiley Inter-Science (www.interscience.wiley.com) DOI 10.1002/tcr.20115

Carbanion Cleavage in 3-Benzoylcyclopropane-1,1,2,2-tetracarbonitrile Effected by Alcoholates

Abstract: R = CH3 (a), CH2CH2OH (b), CH2CH3 (c) Tetracyanocyclopropanes containing five or six electron-withdrawing groups are known to be prone to chemical reactions with nucleophilic reagnts, therewith reactions with hard nucleophiles, alcohols or oximes, occur prevailingly at cyano or acyl groups with retention of the cyclopropane ring, and with soft nucleophiles, with the opening of the cycle However in contrast to this general trend in some reactions with alcoholates and oximates the cycle opening was observed leading to the formation of furan [1–3] or pyrroline [4] derivatives A similar transformation we found studying reactions of 3-benzoylcyclopropane-1,1,2,2-tetracarbonitrile (I) [5] with alcoholates In reaction of compound I with sodium alcoholate in the corresponding alcohol [2-alkoxy-5-amino-4-cyano-

Reações de 1,2-dicloro-4,5-dinitrobenzeno com aminas: monossubstituição de nitro e dissubstituição de cloro e nitro

Abstract: 1,2-dichloro-4,5-dinitrobenzene (DCDNB) reacts with primary and secondary amines, in acetonitrile, at room temperature, to give a monosubstituted nitro product with a yield of 85 to 95%. The chloro-nitro-disubstituted product is formed with excess amine under reflux. Piperidine, pyrroline, dimethylamine and methylamine were the most reactive reagents in both mono- and disubstitution.

Synthesis of New Paramagnetic Fatty Acids and Lipophilic Spin Labels

Abstract: Starting from readily available five-membered cyclic nitrones, paramagnetic analogues of palmitic and hexadec-2 E-enoic acids are described with a range of pyrrolidine ring orientations. Herein we report the synthesis of 3,4-disubstituted lipophilic pyrroline nitroxides through a palladium-catalyzed cross-coupling reaction. Lipophilic phosphonium salt and SH-specific labels (methanethiosulfonates and isoselenuronium salts) with allylic and propargylic terminal groups are also described.

Synthesis of N-Alkylated 4-Fluoro-5-phenylpyrrole-2-carboxylate via Isolable Pyrroline Ionic Intermediates

Abstract: Organic fluorine chemistry produces many useful products. This paper elucidates the reaction of ethyl-4,4- difluoro-2-iodo-5-oxo-5-phenylpentanoate (2) with primary amines in a one-pot scheme. The reaction produced a series of β-fluoropyrrole derivatives at ambient temperatures. In this reaction, the less bulky the primary amine the higher was the resultant yield. When (2) and aqueous methylamine (40%) were allowed to react below 0 oC, 5-(ethoxycarboxyl)-1-methyl-3,3-difluoro-2-hydroxy-2-phenylpyrrolidine, an intermediate molecule for 2-ethyl-4-flouro-1-methyl-5-phenylpyrrole-2-carboxylate (5), was isolated first. Then, (5) reacted with hydroperchloric acid and acetic anhydride to form 5-(ethoxycarboxyl)-1-methyl-3,3-difluoro-2- phenylpyrrolinium perchlorate (6), which was converted to 2-ethyl-4-flouro-1-methyl-5-phenylpyrrole-2- carboxylate gradually in the presence of a base. Our experiments demonstrate that the formation of 2-ethyl-4- flouro-1-methyl-5-phenylpyrrole-2-carboxylate occurs via both one-pot schemes and stepwise pathways, depending on the reaction conditions. The isolation and characterization of the isolated intermediate (6) suggest an anionic pathway for this reaction.

Dibasic or tribasic N-acyl-2,3-pyrroline compound and its synthesis

Abstract: A bisubstituted or trisubstituted N-acyl-2,3-bihydropyrrole compound is prepared from the diiodo compound, amide or aminoester, and catalyst (Cu salt and inorganic alkali) Its preparing process is also disclosed

Reaction of Functionalized Azomethine Ylides with Olefinic Dipolarophiles.

Abstract: N-Unsubstituted pyrrolidine derivatives are prepared by the cycloaddition of an N-unsubstituted azomethine ylide in the pyrido[1,2-a]pyrimidin-4(4H)-one system and olefinic dipolarophiles. The acid treatment of the cycloadducts, pyrrolidines, caused a fission reaction to give pyrroline derivatives and the parent heterocyclic system.