- A new access to pyrrolizidine derivatives: Ring contraction of methyl (E)-[1,2-oxazin-3-yl]propenoates
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Nitrosoalkene 2 generated in situ from oxime 3 underwent smooth hetero Diels-Alder reaction with enol ethers 1 to afford 1,2-oxazine derivatives 4 bearing an exocyclic C=C bond. Methoxyallene 8 and 2 provided 6H-1,2-oxazine 10 in good overall yield. The exocyclic double bond of this type of 1,2-oxazines can be employed for addition reactions as demonstrated by dihydroxylation of 4a with potassium permanganate, smoothly delivering 1,2-diol 11. A reductive cascade reaction involving ring cleavage at the N-O bond followed by cyclization steps furnished pyrrolizidinone derivatives 12 in good yields. In the case of 12b this transformation proceeded with excellent stereoselectivity. Finally, the lactam moiety of 12 could be reduced with borane to provide the corresponding pyrrolizidine derivatives 19 in good yield. Georg Thieme Verlag Stuttgart.
- Zimmer, Reinhold,Collas, Markus,Czerwonka, Regina,Hain, Ute,Reissig, Hans-Ulrich
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- Rapid Synthesis of Bicyclic N-Heterocyclic Cores from N-Terminal α,β-Unsaturated Diazoketones
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A method for the synthesis of bicyclic N-heterocyclic cores from N-terminal α,β-unsaturated diazoketones has been developed. The transformation involves three sequential steps that include N-deprotection, an intramolecular aza-Michael, and a photochemical Wolff rearrangement as a one-pot protocol. By using this strategy, a series of substituted bicyclic N-heterocycles, particularly, indolizidines and pyrrolizidines, were synthesize in good yields.
- Santiago, Jo?o Victor,Burtoloso, Antonio C. B.
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p. 2822 - 2830
(2018/06/04)
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- Hydrogenation of pyrrolizin-3-ones; New routes to pyrrolizidines
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Pyrrolizin-3-ones (e.g.1) can be easily hydrogenated to their hexahydro (pyrrolizidin-3-one) derivatives in the presence of heterogeneous catalysts. Good diastereoselectivity (up to >97:3, depending on catalysts and solvent) can be achieved if the pyrroli
- Despinoy, Xavier L. M.,McNab, Hamish
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experimental part
p. 4502 - 4511
(2009/12/25)
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- Radical Carboazidation: Expedient Assembly of the Core Structure of Various Alkaloid Families
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A procedure for one-pot intermolecular radical addition of 2-iodoesters to terminal alkenes followed by azidation of the radical adduct has been developed. This sequential reaction represents an alkene carboazidation process. Its efficacy is demonstrated
- Panchaud, Philippe,Ollivier, Cyril,Renaud, Philippe,Zigmantas, Sarunas
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p. 2755 - 2759
(2007/10/03)
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- Evaluation of pyrrolidin-2-imines and 1,3-thiazolidin-2-imines as inhibitors of nitric oxide synthase
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Syntheses and evaluation of pyrrolidin-2-imines and 1,3-thiazolidin-2- imines as inhibitors of nitric oxide synthase (NOS) are discussed. An extensive SAR was established for pyrrolidin-2-imines class of compounds. The amidines came out as the most potent inhibitors in addition to displaying selectivity.
- Shankaran,Donnelly, Karla L.,Shah, Shrenik K.,Guthikonda, Ravindra N.,MacCoss, Malcolm,Humes, John L.,Pacholok, Stephen G.,Grant, Stephan K.,Kelly,Wong
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p. 4539 - 4544
(2007/10/03)
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- Radical carboazidation of alkenes: An efficient tool for the preparation of pyrrolidinone derivatives
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A one-pot intermolecular radical carboazidation of alkenes is reported. The utility of the reaction is demonstrated by the development of a three-component preparation of pyrrolidinones, pyrrolizidinones [Eq. (a)], and indolizidinones starting from benzen
- Renaud, Philippe,Ollivier, Cyril,Panchaud, Philippe
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p. 3460 - 3462
(2007/10/03)
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- α-(N-carbamoyl)alkylcuprate chemistry in the synthesis of nitrogen heterocycles
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The conjugate adducts obtained via coupling of α-(N-carbamoyl)alkylcuprates with α,β-ynoates, α-allenyl esters, or α,β-enoates or enimides undergo N-Boc deprotection and cyclization onto the ester functionality upon treatment with PhOH/TMSCl, catecholboron bromide, or trimethylsilyl triflate. This two-pot sequence provides synthetic routes to 4-alkylidinepyrrolidine-2-ones, 4-alkylidinepyrrolizidin-2-ones, and 4-alkylidineindolizidin-2-ones via allenyl esters; pyrrolin-2-ones, tetrahydropyrrolizin-2-ones, and tetrahydroindolizin-2-ones via α,β-ynoates; pyrrolidin-2-ones, pyrrolizidin-2-ones, and indolizidin-2-ones via α,β-enoates or α,β-enimides. The reluctance of γ-carbamoyl-α,β-enoates to undergo E/Z isomerization requires the use of (Z)-β-iodo-α,β-enoates readily prepared by the addition of HI to the alkynyl esters for the efficient preparation of pyrrolinones, tetrahydropyrrolizinones, and tetrahydroindolizinones. Utilization of ω-functionalized α,β-ynoates or β-iodo-α,β-enoates allows for cyclization onto the ω-functionality providing for a synthetic route to quinolizidines.
- Dieter, R. Karl,Lu, Kai
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p. 847 - 855
(2007/10/03)
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- Formation of lactams via photoelectron-transfer catalyzed reactions of N-allylamines with α,β-unsaturated esters
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Anthraquinone photosensitized reactions of a few N-allylamines with α,β-unsaturated esters have been investigated. These reactions led predominantly to the formation of lactams along with trace amounts of products arising out of tandem radical addition reactions. A mechanism is proposed involving the rearrangement of the α-aminoallyl radical, initially generated via anthraquinone photosensitized reactions, to α-aminoalkyl radicals. Subsequent reactions of these radicals with α,β-unsaturated esters can lead to the observed products.
- Das, Suresh,Dileep Kumar,Shivaramayya, Kalchar,George, Manapurathu V.
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p. 3425 - 3434
(2007/10/03)
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- Anthraquinone-photocatalysed addition of amines toα,β-unsaturated esters: a novel route to indolizidone, pyrrolizidone and related ring systems
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The indolizidone 9, the pyrrolizidone 14, a mixture of heliotridone 15a and pseudoheliotridone 15b and the lactam 19 have been synthesized in a one-step anthraquinone-photocatalysed reaction of the corresponding amines, piperidine 1, pyrrolidine 10 and morpholine 16, with α,β-unsaturated esters.
- Das, Suresh,Kumar, J. S. Dileep,Shivaramayya, K.,George, M. V.
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p. 1797 - 1800
(2007/10/02)
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- Bicyclization of aza-compounds by positive halide ions. II. Lactams and some related cyclizations
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Anodic oxidation of lactams in the presence of halide ions produced excellent yields of bicyclic compounds with reactants having rings in the range of eight to ten atoms (C7 to C9).Smaller rings did not react to form bicyclic products and larger rings gave reduced yields.Attempts were made to cyclize non-cyclic amides and to bicyclize cycloheptyl and cyclooctyl acetamide with limited success.
- Elofson, Richard M.,Gadallah, Fahmi F.,Laidler, James K.
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p. 2770 - 2773
(2007/10/02)
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