Photochemistry of .alpha.-pyrone in solid argon

Pong, Richard G. S.; Shirk, James S.

doi:10.1021/ja00782a049

Cited by 63 publications

(41 citation statements)

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“…[20][21][22][23][24][25] Such thermal ring openings of the pyran-2-one ring have been shown to occur across a rather low barrier, which was explained by the pseudopericyclic nature of the transition state. [7][8][9][10][11][12][13][14][15][16][17][18][19]29] By laser ultraviolet irradiation of α-pyrone, [24] the reverse reaction, i.e.…”

Section: Resultsmentioning

confidence: 99%

“…(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) thiadiazoles, 1,2,3-triazoles and 1,2,3-thiadiazines [4][5][6] we have studied the cyclizations of 2-diazothioacetamides and 2-diazoamidines by experimental and theoretical methods. [4,5] Based on previous knowledge of the mechanisms of electrocyclic reactions of ketenes [7][8][9][10][11][12][13][14][15][16][17][18][19] and on known facts of their formation from pyran-2-ones [20][21][22][23][24][25] we anticipated 6aminopyran-2-ones to be good precursors for the generation of carbamoylketene intermediates that can recyclize by interaction of the ketene moiety with the nitrogen atom of the amido group to form the isomeric 6-hydroxypyridin-2ones.…”

Section: Introductionmentioning

confidence: 99%

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Synthetic and Theoretical Aspects of New Dimroth Rearrangement of6‐Aminopyran‐2‐ones to 6‐Hydroxypyridin‐2‐ones via Carbamoyl Ketenes

Subbotina¹,

Fabian

Tarasov³

et al. 2005

Eur J Org Chem

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Two alternative directions for thermal transformation of 6-amino-4-oxopyrano [3,4-d] [1,2,3]thiadiazoles 1, leading either to 6-hydroxy-4-oxo-[1,2,3]thiadiazolo[4,5-c]pyridines 2 or 2-cyano-2-(1,2,3-thiadiazol-5-yl)acetamide 4b, were observed. The first one represents a new, Dimroth-type rearrangement and proceeds by thermal opening of the pyrane ring, followed by the simultaneous rotational isomerization of the ketene intermediate 7 (s-cis) to 7 (s-trans) and its recyclization onto the amido group to form the pyridin-2-one cycle. The first step of the rearrangement has a calculated [B3LYP/ 6-31G(d)] activation barrier of 24-34 kcal/mol, the involve-

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Synthetic and Theoretical Aspects of New Dimroth Rearrangement of6‐Aminopyran‐2‐ones to 6‐Hydroxypyridin‐2‐ones via Carbamoyl Ketenes

Subbotina¹,

Fabian

Tarasov³

et al. 2005

Eur J Org Chem

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“…The ring-opening photochannel strongly dominates over the Dewar formation in a non-substituted a-pyrone [12][13][14][15][16][17]. Addition of substituents may alter the photochemistry of the pyrone ring.…”

Section: Introductionmentioning

confidence: 99%

UV-induced photochemistry of methyl coumalate (methyl 2-pyrone-5-carboxylate) isolated in low-temperature inert matrices

Reva

Nowak

Lapiński

et al. 2006

Chemical Physics Letters

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Photochemical transformations of methyl coumalate have been studied by matrix-isolation technique. Two photoreactions were induced by UV (k > 295 nm) light: isomerisation to the Dewar form and a-bond cleavage leading to the open-ring aldehyde-ketene. The first photoprocess was found to be strongly dominating. Experimental evidence of photoreversibility of both photoisomerisation processes has been provided. Upon k > 200 nm irradiation, the photochemically formed monomeric Dewar species underwent decarboxylation, with production of methoxycarbonyl-substituted cyclobutadiene. This antiaromatic photoproduct was experimentally observed for the first time. All the photoproduced species were identified by comparison of their IR spectra with the spectra calculated at the DFT(B3LYP)/6-311++G(d,p) level.

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“…16 The classic examples of such a reaction leading to conjugated ketenes as primary photoproducts are those observed for 2,4-cyclohexadienone [17][18][19][20] and R-pyrone. [21][22][23] For these compounds, the single bond (C-C or C-O) is cleaved upon UV excitation. The production of conjugated ketenes as direct photoproducts was proven by observation of characteristic, very intense bands at ca.…”

Section: Introductionmentioning

confidence: 99%

Photochemical Ring-Opening Reaction in 2(1H)-Pyrimidinones: A Matrix Isolation Study

et al. 2003

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Photoreactions induced by UV-B (290-320 nm) irradiation were studied for 1-methyl-2(1H)-pyrimidinone and 1-methylcytosine monomers isolated in low-temperature inert gas matrixes. A Norrish type I R-cleavage reaction leading to open-ring conjugated isocyanate was observed for 1-methyl-2(1H)-pyrimidinone. The structure of the photoproduct was identified by comparison of its experimental IR spectrum with the spectrum theoretically calculated at the DFT(B3LYP)/6-31++G(d,p) level. The main indication of isocyanate as a photoproduced species was the appearance in the infrared spectrum recorded after UV irradiation of a very strong band at a characteristic frequency of 2263 cm -1 . Observation of a new band at nearly the same frequency in the spectrum of UV-irradiated monomeric 1-methylcytosine may suggest that also in the case of this compound a conjugated isocyanate is photoproduced.

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Photochemistry of .alpha.-pyrone in solid argon

Cited by 63 publications

References 1 publication

Synthetic and Theoretical Aspects of New Dimroth Rearrangement of6‐Aminopyran‐2‐ones to 6‐Hydroxypyridin‐2‐ones via Carbamoyl Ketenes

Synthetic and Theoretical Aspects of New Dimroth Rearrangement of6‐Aminopyran‐2‐ones to 6‐Hydroxypyridin‐2‐ones via Carbamoyl Ketenes

UV-induced photochemistry of methyl coumalate (methyl 2-pyrone-5-carboxylate) isolated in low-temperature inert matrices

Photochemical Ring-Opening Reaction in 2(1H)-Pyrimidinones: A Matrix Isolation Study

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