Molecular photochemistry. XLVIII. Type I and type II photochemical reactions of some five- and six-membered cycloalkanones

Dalton, J. Christopher; Dawes, K.; Turro, N. J.; Weiss, David S.; Barltrop, J. A.; Coyle, J. D.

doi:10.1021/ja00755a016

Cited by 80 publications

(23 citation statements)

References 14 publications

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“…quite similar (Table 1), the rate of fluorescence The smaller value of O'F for TBK is attributed to of these two ketones should be almost the same the occurrence of a competing fast hydrogen-atom [22,23]. We also assume that the rates of ISC abstraction reaction from the excited singlet state.…”

Section: Of(dbk) Kfmentioning

confidence: 93%

“…We conclude that the RP 1) shows that the maximum extinction coefficient from aa'-dimethyl dibenzyl ketone should be simof the n,7r* band is generally ten times that for ilar to that from DBK, so that an efficient cage acetone. Thus it is expected that the radiative rate recombination following a-cleavage in S, of DBK constant of fluorescence kF should be about ten times larger for DBK.than for acetone [22,23]. 5 shows a quantum yield of fluorescence cornThus if the rate constant of ISC for DBK follows parable with that of DBK and therefore does not the trend for alkyl-substituted acetones, and dedisplay any special pathways for deactivation of creases relative to acetone, the quantum yield of S 1 .…”

Section: 5mentioning

confidence: 99%

“…Acknowledgments are expected to be similar [22,23]. The relative fluorescence quantum yield of 3 is 0.16 that of…”

mentioning

confidence: 99%

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Singlet state photochemistry of dibenzyl ketone and its o-tolyl derivatives

Noh

Step

Turro

1993

Journal of Photochemistry and Photobiology A: Chemistry

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Section: Of(dbk) Kfmentioning

confidence: 93%

Section: 5mentioning

confidence: 99%

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Singlet state photochemistry of dibenzyl ketone and its o-tolyl derivatives

Noh

Step

Turro

1993

Journal of Photochemistry and Photobiology A: Chemistry

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“…This is presumably because the hydrogens of the methoxyl group are held distant from the n-orbitals of the carbonyl group and thus do not satisfy the strict geometrical requirements for Norrish I1 cleavage (22).…”

Section: Modes Of Photoreaction Of A-ketols Arzrl Related Cotnpoundsmentioning

confidence: 99%

“…As for the related oxygensubstituted ketones, a mechanism comprising a-cleavage and hydrogen abstraction in the resulting diradical 50 and intramolecular addition to the ketene intermediate 51 is considered to account best for the formation of 46 (Scheme 7). a-Dialkylamino cyclohexanone systems have been observed to undergo direct P-cleavage of the C-N bond (23), while hydrogen abstraction becomes a competitive process for a-dialkylamino ketones, where a-hydrogens that are geometrically favorably disposed (22) are available (24). To the best of our knowledge, the formation of amide 46 from irradiation of amino ketone 45 represents the first example of an a-cleavage reaction of an a-amino ketone.…”

Section: Modes Of Photoreaction Of A-ketols Arzrl Related Cotnpoundsmentioning

confidence: 99%

Photochemistry of cyclic α-hydroxy ketones. I. The nature and genesis of the photoproducts from steroidal 5-hydroxy 6-keto steroids and related compounds

Stiver¹,

Yates²

1988

Can. J. Chem.

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14 (1988). Photolyses of 5-hydroxy-5a-and 5P-cholestan-6-one and their 3P-acetoxy-and 30-benzyloxy derivatives in benzene or ethanol proceed stereospecifically with retention of configuration at C-5 to give the corresponding lactones, 6-oxa-Bhomocholestan-7-ones. Photolyses of 3P-acetoxy-7a-deutero-5-hydroxy-5a-and 50-cholestan-6-ones also proceed stereospecifically to give the corresponding 5-deutero lactones. 3~-Acetoxy-5-deuteroxy-5a-and SP-cholestan-6-one give on irradiation 1:3 and 7 : l mixtures, respectively, of the corresponding 7 a a -and 7aP-deutero lactones. Irradiation of 3~-acetoxy-5-methoxy-5a-cholestan-6-one in ethanol leads to the stereoselective formation of ethyl 3P-acetoxy-5-methoxy-5,6-seco-5a-cholestan-6-oate, while that of 3P-acetoxy-Sa-cholestan-6-one gives mainly photoreduction products. These observations are interpreted in terms of a-cleavage of the C-5-C-6 bond of the ketols to give alkyl acyl diradicals that undergo hydrogen transfer to give hydroxy ketenes, which then form the lactones. It is proposed that retention of configuration at C-5 results from two major factors-the nonplanar geometry of the hydroxyalkyl radical center, and fast hydrogen transfer in the diradical, the latter resulting from restricted rotation about the C-9-C-10 bond. The specific transfer of the 7a-deuterium atom in the 7a-deutero ketols is attributed to these factors and to the preferred direction of opening to the diradical on a-cleavage. The 0-deuterium labelling results are interpreted in terms of product development control in the conversion of the hydroxy ketenes to the lactones and are in accord with restricted rotation about the C-9-C-I0 bond. The photolysis of 3P-acetoxy-5-amino-5a-cholestan-6-one proceeds stereoselectively to give the SP-lactam analogue of the SP-lactone formed from the analogous Sa-ketol.SHIRLEY STIVER et PETER YATES. Can. J. Chem. 66, 214 (1988). La photolyse des hydroxy-5 5 a -et SP-cholestanones-6 et de leurs dCrivCs acCtoxy-3P et benzyloxy-3P, dans le benzkne ou I'tthanol, se produit d'une faqon stCrCospCcifique, avec rCtention de configuration en C-5, pour conduire aux lactones correspondantes, oxa-6 B-homocholestanones-7. La photolyse des acCtoxy-3P deutCro-7a hydroxy-5 5 a -et SP-cholestanones-6 se produit aussi d'une faqon stCrCospCcifique pour conduire aux lactones correspondantes deutkro-5. Par irradiation, les acCtoxy-3P deutCroxy-5 5 a -et 5P-cholestanones-6 conduisent respectivement a des melanges 1:3 et 7:l des lactones correspondantes deutCro-7aa et -7aP. L'irradiation de I'acCtoxy-3P mCthoxy-5 5a-cholestanone-6, dans I'Cthanol, conduit la formation stCrCosClective de I'acCtoxy-30 mCthoxy-5 sCco-5,6 5a-cholestanoate-6 d'Cthyle alors que celles de I'acetoxy-3P 5a-cholestanone-6 donne principalement des produits de photorCduction. On interprkte ces rCsultats en fonction d'un clivage-a de la liaison C-5/C-6 des cCtols qui fournit des diradicaux alkyle acyle qui subissent des transferts d'hydrogene conduisant des hydroxy-cCtenes qui forment alors des lactones. On suggkr...

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Solution‐Phase Photochemistry of Cyclobutanones

Morton

Turro

1974

Advances in Photochemistry

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Molecular photochemistry. XLVIII. Type I and type II photochemical reactions of some five- and six-membered cycloalkanones

Cited by 80 publications

References 14 publications

Singlet state photochemistry of dibenzyl ketone and its o-tolyl derivatives

Singlet state photochemistry of dibenzyl ketone and its o-tolyl derivatives

Photochemistry of cyclic α-hydroxy ketones. I. The nature and genesis of the photoproducts from steroidal 5-hydroxy 6-keto steroids and related compounds

Solution‐Phase Photochemistry of Cyclobutanones

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