Die 1,3-Dipolare Cycloreversion von 1-Azetinen

Burger, Klaus; Thenn, Willy; Müller, Evi

doi:10.1002/ange.19730850312

Cited by 11 publications

(4 citation statements)

References 7 publications

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“…Neben 30 mg la, das aus der schneller laufenden Zone isolicrt wurde, erhielt man aus ciner zwciten, langsanier lauicnden Zonc 348 mg (54%) 15, das nach 2maligcr Utikristallisation aus HexanlAther eincn Smp. von 85,7 (17), 103 (24). 102 (17), 91 (14j, 89 (6).…”

Section: Trans-17unclassified

Photochemische Cycloadditionen von 3‐phenyl‐2h‐azirinen mit Aldehyden. 31. Mitteilung über Photoreaktionen

Giezendanner

Heimgartner

Jackson

et al. 1973

Helvetica Chimica Acta

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Experiments concerning the photochemical condensation of 3-phenyl-2 H-azirines 1 with aliphatic and aromatic aldehydes to 3-oxazolines 4 are fully described (cf. scheme 1). Photochemically nitrile methylides of type 2 are first formed, which then very quickly react thermally with the aldehydes in a regiospecific manner to give the 3-oxazolines 4. Azirines monosubstituted in position 2 ( l b and Ic) give mixtures of cis, trans-oxazoline isomers, in which the cis isomer predominates. The stereoselectivity of the cycloaddition reaction can be rationalized by a simple model (scheme 10).The stereoisomeric 3-oxazolines 4 are distinguishable in the NMR. spectra by the large homoallylic coupling constants between the H atoms on C(2) and C(5) 1. Einleitung. -In einer vorlaufigen Mitteilung [2] berichteten wir vor kurzem uber die Bildung von 3-Oxazolinen 4 bei der Bestrahlung von 3-Phenyl-2 H-azirinen I) 30.Mitteilung siehe [l].

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Section: Trans-17unclassified

Photochemische Cycloadditionen von 3‐phenyl‐2h‐azirinen mit Aldehyden. 31. Mitteilung über Photoreaktionen

Giezendanner

Heimgartner

Jackson

et al. 1973

Helvetica Chimica Acta

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“…[3]), for example with alcohols, clearly indicates where the highest electron density in the HOMO is located. Benzonitrilio-dialkylmethanides (1; R' = Ph, R2, R3 = alkyl), for example, are protonated at C( 1) [4][7][8], but benzonitrilio-bis(trifluoromethy1)methanide (1; K' = Ph, R2, R3 = CF,) is protonated at C(3) [9].Houk's calculations 121 have shown that n-acceptor substituents at C( 1) diminish the energy difference between structures 1A and 1B and, thus, lead to a more linear structure of the nitrile ylide. @Donors at C(1) seem to have a similar effect.…”

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confidence: 99%

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confidence: 99%

Synthesis of 4‐Alkoxy‐1,3‐oxazol‐5(2H)‐ones, Precursors of 1‐alkoxy substituted nitrile ylides

Bozhkova¹,

Heimgartner²

1989

Helvetica Chimica Acta

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4-Alkoxy-l,3-oxazol-5(2H)-ones of type 4 and 7 were synthesized by two different methods: oxidation of the 4-(phenylthio)-l,3-oxazol-5(2H)-one 2a with m-chloroperbenzoic acid in the presence of an alcohol gave the corresponding 4-alkoxy derivatives 4, presumably via nucleophilic substitution of an intermediate sulfoxide (Scheme 2). The second approach is the BF,-catalyzed condensation of imino-acetates of type 6 and ketones (Scheme 3). The yields of this more straightforward method were modest due to the competitive formation of 1,3,5-triazine tncarboxylate 8. At I 55", 1,3-oxazol-5(2H)-one 7b underwent decarboxylation leading to an alkoxy-substituted nitrile ylide which was trapped in a 1,3-dipolar cycloaddition by trifluoro-acetophenone to give the dihydro-oxazoles cis-and rrans-9 (Scheme 4). In the absence of a dipolarophile, 1S-dipolar cyclization of the intermediate nitrile ylide yielded isoindole derivatives 10 (Schemes 4 and 5 ) .

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“…The H atoms on the nitrogen could not be unambiguously located, even by a highangle refinement with subsequent difference Fourier synthesis. In the diagram they have been positioned according to their ideal geometry.-Space group C2/c, 2 = 4 , a = 1482.5 (2), b= 1247.9(4), c= 1866.7(3) pm,p=98.63(2)', @(MoKa) = 0.64 mm -', R = 0.055, R , = 0.054 ( w -' = ( ~' ( 0 + 0.0002 9). Further details of the crystal structure investigation are available on request from the Fachinformationszentrum Energie, Physik, Mathematik GmbH, D-7514 Eggenstein-Leopoldshafen 2 (FRG), on quoting the depository number CSD-52 105, the names of the authors, and the full citation of the journal.…”

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confidence: 99%