Pyrrolizidin‐Synthesen, III

Flitsch, Wilhelm; Hampel, K. E.

doi:10.1002/jlac.198819880503

Cited by 22 publications

(4 citation statements)

References 10 publications

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“…These two experiments gave a 78:22 and a 71:29 ratio of 10 : 9 , respectively, indicating the greater stability of 10 relative to 9 . Although 10 has been reported in the literature, 9c, no spectral data is available, and we were unable to separate 9 and 10 by silica gel or alumina chromatography. Nonetheless, GC−MS analysis of a mixture of 1 : 9 : 10 (determined by NMR analysis) showed two separate ion-current peaks, each of which displayed a similar mass spectrum indicative of isomers.…”

Section: Resultsmentioning

confidence: 86%

Synthesis of (−)-(R)-Pyrrolam A and Studies on Its Stability: A Caveat on Computational Methods

et al. 2004

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The asymmetric synthesis of (-)-(R)-pyrrolam A was achieved in three operations from N-Boc pyrrolidine via an alpha-(N-carbamoyl)alkylcuprate vinylation reaction followed by N-Boc deprotection and cyclization. One-pot deprotection-cyclization procedures led to mixtures of pyrrolam A and its double bond isomers. These isomerization events could be circumvented by use of a two-step procedure. To guide aspects of the experiments, a series of computational energy evaluations and chemical shift predictions were performed with molecular mechanics, semiempirical, ab initio, and density functional methods. The relative stabilities of the double bond isomers, as estimated by experiment, challenged a number of computational methods, and only the MP2 model with its moderate degree of electron correlation came close to matching the experimental data. The MP2 method was further applied to an unusual aspect of the double bond migration between pyrrolam A and its isomer 9. The reaction (1 to 9) on neat samples is irreversible without racemization, and the alumina-mediated equilibration is accompanied by complete loss of enantiomeric excess. The source of the irreversibility was traced to asymmetric charge distribution in the intermediate dienolate anion. The analysis ultimately led to a semiquantitative sketch of the pyrrolam energy surface.

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Section: Resultsmentioning

confidence: 86%

Synthesis of (−)-(R)-Pyrrolam A and Studies on Its Stability: A Caveat on Computational Methods

et al. 2004

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“…Phosphorous ylides can be considered strong nucleophiles according to our previous classification because the carbon atom of the ylide can attack the imide carbonyl without any prior activation. Flitsch and co-workers explored an intramolecular Wittig olefination between a succinimide ring and a phosphonium moiety, thus allowing the preparation of a few bicycles 119-122 in synthetically useful yields (Scheme 26), along with other bicyclic structures [77] (not shown).…”

Section: Cyclizations Using Strong Nucleophilic Partnersmentioning

confidence: 99%

Cyclization Strategies Using Imide Derivatives for the Synthesis of Polycyclic Nitrogen‐Containing Compounds

2022

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Cyclization strategies employing imides and their derivatives have attracted the attention of several organic chemists interested in synthesizing polycyclic alkaloids. Numerous strategies have been developed, mostly focused on i) the use of masked iminium ions, ii) addition of weak nucleophiles onto the carbonyl group of the imide being activated by a Lewis or Brønsted acid, iii) addition of strong nucleophiles onto the imide carbonyl, iv) radical-based processes and v) miscellaneous methods. This review is not comprehensive. It aims to provide the reader with a selection of representative synthetic strategies available in the area up to date.

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“…Using a slightly different procedure, a solution of 5methoxymethylene-2,2-dimethyl-1,3-dioxane-4,6-dione 1 (1.86 g, 10 mmol) and 4-methoxy-3-pyrrolin-2-one (1.13 g, 10 mmol) in acetonitrile (10 cm 3 ) was stirred at room temperature for 48 h and the solvent removed to give 5-[1-(4-methoxy-2-oxo-3-pyrrolin-1-yl)]methylene-2,2-dimethyl-1,3-dioxane-4,6-dione 13 (2.41 g, 90%), mp 211 (22), 132 (20), 96 (32), 69 (31) and 41 (37).…”

Section: -[1-(4-methoxy-2-oxo-3-pyrrolin-1-yl)]methylene-22-dimethyl-...mentioning

confidence: 99%

“…(N-Methylformamide, 75 h, chromatography) gave methyl 3-(Nformyl-N-methylamino)prop-2-enoate 21 (11%), mp 85-86 (27), 124 (95), 108 (17), 96 (100), 83 (20) and 70 (34).…”

Section: Methyl 3-(n-formyl-n-methylamino)prop-2-enoate 21mentioning

confidence: 99%

Synthetic routes to pyrrolizine-1,5-dione derivatives by flash vacuum pyrolysis of amidomethylene derivatives of Meldrum's acid

et al. 2009

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Methoxymethylene Meldrum's acid 1 reacts with 5- and 6-membered lactams in refluxing acetonitrile to give the N-substituted products 9-15. If the reactions are continued for extended times, the Meldrum's acid derivatives decompose to provide enamidoesters e.g. 22-24. Flash vacuum pyrolysis of the 5-membered ring products 9-13 provides reasonable yields of the fused pyrrolones 31-35. The constitution of the products is supported by X-ray crystal structures of 10, 12, 19, 32 and 34.

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Pyrrolizidin‐Synthesen, III

Cited by 22 publications

References 10 publications

Synthesis of (−)-(R)-Pyrrolam A and Studies on Its Stability: A Caveat on Computational Methods

Synthesis of (−)-(R)-Pyrrolam A and Studies on Its Stability: A Caveat on Computational Methods

Cyclization Strategies Using Imide Derivatives for the Synthesis of Polycyclic Nitrogen‐Containing Compounds

Synthetic routes to pyrrolizine-1,5-dione derivatives by flash vacuum pyrolysis of amidomethylene derivatives of Meldrum's acid

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