Photochemical transformations of small ring heterocyclic compounds.  XLVII.  Electronic details of the photocycloaddition of arylazirines

Padwa, Albert; Dharan, Murali; Smolanoff, Joel; Wetmore, S. I.

doi:10.1021/ja00787a040

Cited by 68 publications

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“…This procedure has been widely used in the synthesis of a variety of five-membered heterocycles (cf., Scheme 1). [5][6][7][24][25][26][27] Recent quantum-chemical calculations shed some light on the above-mentioned observations. On the basis of complete active space self-consistent field (CASSCF) calculations, Klessinger and Borneman 28,29 demonstrated that the photochemical formation of the nitrile ylide from the respective 2H-azirine (by C-C bond cleavage) occurs in an nπ* singlet excited state and involves a barrierless conical intersection between the S 1 and S 0 potential energy surfaces.…”

Section: Introductionmentioning

confidence: 99%

Methyl 3-Methyl-2H-azirine-2-carboxylate Photochemistry Studied by Matrix-isolation FTIR and DFT Calculations

et al. 2006

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The aliphatic 2H-azirine, methyl 3-methyl-2H-azirine-2-carboxylate (MMAC), has been synthesized and its monomeric form investigated by IR spectroscopy in an argon matrix, at 10 K, as well as theoretically (DFT/ B3LYP/6-311++G(d,p)). Two low-energy conformers of MMAC (Ct and Cc) were found in the matrix, both exhibiting the cis conformation around the C-O bond but differing in the arrangement around the C-C R bond. The two conformers were photoreactive upon in situ broadband UV excitation (λ > 235 nm), yielding nitrile ylide (P1) and ketene imine (P2) type products, which resulted from cleavage of the C-C or C-N bond, respectively. The kinetics of the reactions leading to the formation of P1 and P2 are of first order, with the processes being favored when the reactant is in the Cc conformation. Very interestingly, the C-N bond photocleavage, which is unusual for aliphatic 2H-azirines, was found to be preferred over the generally favored in 2H-azirines C-C bond breakage. This behavior is attributed to the presence in the molecule of the electronwithdrawing methoxycarbonyl substituent, which accelerates the intersystem crossing toward the T 1 triplet state and, in this way, favors the C-N bond cleavage. In addition to the primary photoprocesses leading to formation of P1 and P2, secondary photoprocesses leading to the decarboxylation and decarbonylation of P2 have been also observed.

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Section: Introductionmentioning

confidence: 99%

Methyl 3-Methyl-2H-azirine-2-carboxylate Photochemistry Studied by Matrix-isolation FTIR and DFT Calculations

et al. 2006

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“…C, C(3a) und C(8a)); 77,9 ( 8 , C (1) (6), 256 (8), 202 (lo), 198 (14), 197 (16), 189 (6), 183 (7), 141 (9), 128,5 (lo), 127 (12), 77 (15). (25), 274 (28), 261 (14), 145 (43), 104 (26), 77 (22). 76 (15).…”

Section: Experimenteller Teilunclassified

“…Dies ist durch eine Vielzahl von Beispielen (vgl. [7]) und insbesondere durch die relativen Geschwindigkeitskonstanten der I, 3-dipolaren Cycloadditionen von Benzonitrilio-phenylmethanid (2 a) an Olefine mit n-Akzeptorsubstituenten [22] sowie von Benzonitrilio-2-propanid (2 b) rnit der Carbonylgruppe von a-halogenierten Essigsauremethylestern [ 111 belegt worden. Andererseits mussten Substituenten, welche die HOMO-Energie des Nitrilylids erhohen, d. h. Donorsubstituenten des Dipols, die 1,3-dipolare Cycloaddition beschleunigen (vgl.…”

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Spirocyclische 3‐Oxazoline durch 1,3‐dipolare Cycloaddition von Benzonitrilio‐2‐propanid mit 1,4‐Chinonen

Stegmann

Uebelhart

Heimgartner

1983

Helvetica Chimica Acta

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On irradiation with light of wavelength 290-350 nm, 2,2-dimethyl-3-phenyl-2 H-azirine (lb) reacts with 1,4-naphthoquinone to give the 1H-benzo Iflisoindol-4,9-dione (11) (Scheme 3) via cycloaddition of the benzonitrilio-2-propanide (2 b) onto the quinone C, C-double bond. With 2-methyl-and 2,3-dimethyI-l, 4-naphthoquinone, the nitrile ylide 2 b undergoes cycloaddition preferentially onto the C, 0-double bond of the quinone, leading to spiro-oxazolines 12 and 14 (Scheme 4 ) . Steric as well as electronic effects can be discussed to explain the observed site selectivity of the cycloaddition.With the 1,4-benzoquinones 15a, 15b, 15d and 15f, nitrile ylide 2b undergoes the 1,3-dipoIar cycloaddition exclusively onto the C, 0-double bond. The corresponding spiro-oxazolines have been isolated in 17-32% yield. This contrasts with the previously reported results with benzonitrilio-phenylmethanide (2 a), which undergoes cycloaddition to the C, C-double bond of 1,4-benzoquinones (cf. [ 11). This difference in the site selectivity of the 1,3-dipolar cycloaddition can be explained with Houk's concept of LUMO-polarization, that is, the stronger nucleophilic dipol2 b polarizes the LUMO of a a,P-unsaturated carbonyl compound more efficient than the less nucleophilic 2 a.This leads to a preference of the cycloaddition to the C,O-double bond in the case of 2b.With 2,3-dimethyI-(15c) and 2,3,5,6-tetramethyl-l, 4-benzoquinone (15e), nitrile ylide 2 b undergoes C, 0as well as C, C-cycloaddition (Schemes 7 and 8 ) .1. Einleitung. -Vor einiger Zeit haben wir uber photochemisch induzierte Cycloadditionen von 2,3-Diphenyl-2H-azirin (la) mit 1,4-Chinonen berichtet [ 11. Bei dieser Reaktion werden durch 1,3-dipolare Cycloadditionen des bei der Photolyse von l a ') *) Vorgetragen von H. H. an der Euchem-

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“…Der durch Photolyse in benzolischer Losung aus 1-Azido-1-phenyl-propen erzeugte Dipol 2c [lo] lieferte mit dem 7,5fachen Uberschuss an Aceton das Addukt 8 nur in bescheidener Ausbeute (16,5y0). Nach Padwa et al [8] ergibt die Photoaddition von Aceton und 2,3-Diphenyl-2H-azirin (lb) (2 : 1 Benzol/Aceton-Losung ; ca. 480facher Acetoniiberschuss) das korrespondierende 3-Oxazolin in einer Ausbeute von knapp 40%.…”

Section: Bestrahlung Von 3-phenyl-2h-azirinen In Gegenwart Vonunclassified

“…With various ketones benzonitrile-isopropylide (2a) gives cyclo-addition products in very good preparative yields (scheme I ) . and benzonitrile-benzylide (2b) [8] react, however, sluggishly with ketones, smooth cyclo-addition being observed in their case only with Pactivateds ketones (2,2,2-trifluoro-acetophenonc, 1,1,1-trifluoro-2-propanone). With la acetonylacetonc forms the bis-adduct 12.…”

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confidence: 99%

Photochemische Cycloadditionen von 3‐Phenyl‐2H‐azirinen mit Ketonen, Acylcyaniden und Ketoestern. 33. Mitteilung über Photoreaktionen

Claus

Gilgen

Hansen

et al. 1974

Helvetica Chimica Acta

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Summary. Similarly to aldehydes [6j ketones form 3-oxazolines via cyclo-addition to the benzonitrile-methylides 2 that arise photochemically from the 3-phenyl-2H-azirines 1. With various ketones benzonitrile-isopropylide (2a) gives cyclo-addition products in very good preparative yields (scheme I ) . and benzonitrile-benzylide (2b) [8] react, however, sluggishly with ketones, smooth cyclo-addition being observed in their case only with Pactivateds ketones (2,2,2-trifluoro-acetophenonc, 1,1,1-trifluoro-2-propanone). With la acetonylacetonc forms the bis-adduct 12.While the azirine la reacts with cyclohexanone to yield essentially only the spiro-(3-oxazoline) 13, i t gives with cyclopentanone, depending on the reaction conditions, either the spiro-(3-oxazoline) 14 or the butenyl-3-oxazoline 15 (scheme 3). The formation of 15 has to be preceded by the photochemical formation of 4-pentenal from the ketone. Norcamphor and camphor react in a similar way (schemes 4 and 5 ) .The azirines la-c react smoothly with the kefo groups in acylcyanides and a-keto-esters, giving with the former 5-cyano-3-oxazolines and with the latter 5-ethoxycarbonyl-3-oxazolines (schemes 6 and 7 ) .p-Keto-esters (acetoacetic ester) form with the dipole arising from la the expected addition product 31 and, via the protonated dipole d (scheme 8), finally the benzylidene-acetoacetic ester. Analogous results are obtained with malonodinitrile, trifluoro-acetamidc and other weak acids such as alcohols [29] [30] (scheme 9).The light-induced rearrangement of the bicyclic isoxazoline 37 into the oxazoline 38 is visualized as an intramolecular cyclo-addition reaction (scheme 70). The cyclo-addition in this case proceeds with the aldehyde group inversed as compared to the related intermolecular benzonitrileinethylide addition to aldehydes.Wie in fruheren Arbeiten gezeigt wurde, werden 3-Phenyl-2H-azirine vom Typ 1 durch Licht der Wellenlange ca. 300 nm in Benzonitril-methylide vom Typ 24) umgewandelt, die thermisch mit zahlreichen Dipolarophilen unter Cycloaddition zu funfl) 32. Mitteilungsiehe [l]. *) 3, 4,Gegenwartige Adresse: Organisch-chemisches Institut der Universitat, A 1090 Wien. Neue hdresse : Institut dc chimie organique de l'Universit6, CH-1700 Fribourg, P6rolles. I n dieser Arbeit werden die Benzonitril-methylide(-isopropylide, -benzylide, usw.) in den Schemata stets in der dipolaren Form 2 geschrieben. Streng genommen ware, nach den IUPACNomenklaturregeln, die Bezeichnung ((Methylidea usw. nur auf die zu 2 mesomere Formel mit negativer Ladung auf dem Ylid-Kohlenstoffatom : anwendbar. HELVETICA CHIMICA ACTA -1. 01, 57, Fasc. 7 (1974) -Kr. 236 gliedrigen Heterocyclen abreagieren [Z-81. Im folgenden berichten wir iiber die Reaktionen der Phenylazirine mit Ketonen, Acylcyaniden und Ketoestern. Ketonen. -((Aktivierte)) Ketone wie Z,Z,Z-Trifluor-acetophenon und 1, 1, 1-Trifluor-Z-propanon addieren sich glatt an die aus den 3-Phenyl-2H-azirinen l a und l b photochemisch in Benzollosung mit einer Quecksilber-Hochdrucklampe hinter Pyrex erzeugte...

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Photochemical transformations of small ring heterocyclic compounds. XLVII. Electronic details of the photocycloaddition of arylazirines

Cited by 68 publications

References 0 publications

Methyl 3-Methyl-2H-azirine-2-carboxylate Photochemistry Studied by Matrix-isolation FTIR and DFT Calculations

Methyl 3-Methyl-2H-azirine-2-carboxylate Photochemistry Studied by Matrix-isolation FTIR and DFT Calculations

Spirocyclische 3‐Oxazoline durch 1,3‐dipolare Cycloaddition von Benzonitrilio‐2‐propanid mit 1,4‐Chinonen

Photochemische Cycloadditionen von 3‐Phenyl‐2H‐azirinen mit Ketonen, Acylcyaniden und Ketoestern. 33. Mitteilung über Photoreaktionen

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