Heterolytic Photocleavage of Cyclopropanes

Irving, Charles S.; Petterson, R. C.; Sarkar, Ila; Kristinsson, H.; Aaron, C.S.; Griffin, G. W.; Boudreaux, G. J.

doi:10.1021/ja00975a072

Cited by 23 publications

(5 citation statements)

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“…No polar addition products were obtained. 33,34 This result excludes the intermediacy of ionic species in the isomerization. Moreover, irradiation in the presence of 2-propanol or in the presence of 1.0 M ethanethiol in benzene did not cause the reduction of the acetyl group to a 1-hydroxyethyl group.…”

Section: Stationary State Photochemistry Of 12-diarylcyclopropanes Be...mentioning

confidence: 88%

Photochemical C−C Bond Cleavage of 1,2-Diarylcyclopropanes Bearing an Acetylphenyl Group. Generation and Observation of Triplet 1,3-Biradicals

Ichinose¹,

Mizuno²,

Otsuji³

et al. 1998

J. Org. Chem.

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The photochemical properties of 1,2-diarylcyclopropanes bearing an acetylphenyl group were studied by product analysis and laser flash photolysis. All cyclopropanes showed efficient cis−trans photoisomerization followed by inefficient isomerization to 1,3-diarylpropenes. All the products were unquenched by the addition of triplet quencher, 2-methyl-1,3-butadiene (E T ≃ 60 kcal mol-1), whereas molecular dioxygen gave oxygenated products. Triplet 1,3-biradicals generated from a short-lived acetophenone-like triplet (≲1 ns) were observed as intermediates in these reactions through nanosecond laser flash photolysis. Polar substituent effects on the lifetime of the 1,3-biradicals were small, except for a heavy atom effect in the case of Br. Spin−orbit coupling calculations on model 1,3-biradicals show a negligible effect on polar substituent and thus predict a negligible effect on the intersystem crossing rate. Conjugated biradicals in general now seem unlikely to show the “ionic character effect” on intersystem crossing suggested by the work of Salem and Rowland.

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Section: Stationary State Photochemistry Of 12-diarylcyclopropanes Be...mentioning

confidence: 88%

Photochemical C−C Bond Cleavage of 1,2-Diarylcyclopropanes Bearing an Acetylphenyl Group. Generation and Observation of Triplet 1,3-Biradicals

Ichinose¹,

Mizuno²,

Otsuji³

et al. 1998

J. Org. Chem.

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“…With the possible exception of 6 , products of these structure types have precedence in photolysis reactions of cyclopropane systems. Indan derivatives are typical photolysis products of diarylcyclopropanes; − a reaction of this type was first observed in the photolysis of the symmetrical prototype, 1,2-diphenylcyclopropane . The conversion is readily explained via cleavage of the doubly benzylic cyclopropane bond, yielding a 1,3-bifunctional species, 18 , either a biradical (*, # = •) or a zwitterion (* = +, # = −).…”

Section: Discussionmentioning

confidence: 99%

“…The generation of phenylmethylene upon photolysis of diarylcyclopropanes has precedent; irradiation of 1,2-diphenylcyclopropane in methanol generated benzyl methyl ether, which was rationalized via phenylmethylene. , Similarly, irradiation of 2,3-diphenyloxirane gave rise to insertion and addition products of phenylmethylene. When this reaction was carried out at cryogenic temperatures, a carbonyl ylide was identified as an intermediate based on its optical absorption spectra; upon warming to 140 K, this intermediate underwent thermal fragmentation to phenylmethylene…”

Section: Discussionmentioning

confidence: 99%

“…The photochemistry of cyclopropane and derivatives has been of interest for many years; numerous derivatives have been studied under a variety of reaction conditions. − Among the many reaction types established are addition/substitution with ring opening, − geometric isomerization, − ,− ring opening generating alkenes, ring enlargement forming indans, − or fragmentation yielding carbenes. − The pathways to the various products may be formulated via a range of intermediates, including excited singlet 1-3 or triplet states, ,, radical cations, − triplet biradicals, ,, or zwitterions.…”

Section: Introductionmentioning

confidence: 99%

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Photoreactions of trans-1-o-Hydroxyphenyl-2-phenylcyclopropane

Delgado

Espinós

et al. 1999

J. Org. Chem.

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The photochemistry of trans-1-o-hydroxyphenyl-2-phenylcyclopropane, trans-1, was studied under a variety of experimental conditions. Direct irradiation through quartz in cyclohexane gave rise mainly to ring-expanded products, 2-phenyl-3,4-dihydro-2H-benzopyran, 2, 2-benzyl-2,3-dihydrobenzofuran, 3, and 1-o-hydroxyphenylindan, 4. The major products, 2 and 3, are rationalized by intramolecular proton transfer. However, a significant fraction of 3 is formed via ring-opening to cinnamylphenol, 5. An additional product, o-(alpha-cyclohexylmethyl)phenol, 7, suggests fragmentation of trans-1 and (formal) insertion of o-hydroxyphenylcarbene into cyclohexane. Direct irradiation in methanol produced methanol adducts 8 and 9 instead of 2, 3, 4, or 7. Finally, acetone-sensitized irradiation of trans-1 resulted in geometric isomerization to cis-1; this result can be rationalized via a biradical intermediate.

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“…[22][23][24][25][26][27][28][29][30] Anti-Markovnikov functionalization of unactivated cyclopropanes mostly relies on photoinitiated radical processes with generally poor regioselectivity and limited scope. [31][32][33][34][35][36] To the best of our knowledge, anti-Markovnikov hydrohalogenation of cyclopropanes has not been reported.…”

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confidence: 94%