Photochemical ring expansion of cyclic aliphatic ketones.  Cyclobutanones and cyclopentanones

Morton, Douglas R.; Turro, Nicholas J.

doi:10.1021/ja00793a020

Cited by 46 publications

(13 citation statements)

References 13 publications

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“…Different from the photodecomposition in the gas phase, the cyclobutanone in solution (alcohol) was found to undergo photochemical ring expansion to the cyclic acetal in addition to decarbonylation and cycloelimination reactions [15]. The transient intermediate was proposed as a cyclic oxacarbene (1A in Scheme 1) having the five-membered ring structure [16,17].…”

Section: Introductionmentioning

confidence: 99%

Photochemical reaction mechanism of cyclobutanone: CASSCF study

Chen

Song

2003

Int J of Quantum Chemistry

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ABSTRACT:The photochemical reaction channels of cyclobutanone have been studied at the CASSCF level with a 6-31G* basis set. Starting from the n-* excited-state (S 1 ) cyclobutanone, the three reactions can take place: decarbonylation (produce CO and cyclopropane or propylene), cycloelimination (produce ketene and ethylene), and ring expansion (produce oxacarbene). Our computation indicates that decarbonylation products CO and triplet trimethylene are formed on the triplet n-* excited state (T 1 ) in a stepwise way via a biradical intermediate after intersystem crossing (ISC) to T 1 from S 1 . And, then, the triplet trimethylene undergoes a second ISC to the ground state (S 0 ) to produce the singlet trimethylene from which cyclopropane can be produced rapidly only overcoming a 1 to 2-kcal/mol barrier while propylene can be formed as a secondary product. The cycloelimination products ketene and ethylene are formed on the S 0 in a concerted mechanism after internal conversion (IC) to S 0 from S 1 via a biradical conical intersection. The reaction channels corresponding to ring expansion on the S 0 , T 1 , and S 1 states have also been discussed, and the likeliest reaction path is that oxacarbene is formed on the ground state following S 1 /S 0 internal conversion. The surface topology of cyclobutanone on the S 1 surface is characterized by a transition state separating the minimum from the S 1 /S 0 conical intersection, which is consistent with the previous computations and can explain the wavelength dependence of the fluorescence emission yield.

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Section: Introductionmentioning

confidence: 99%

Photochemical reaction mechanism of cyclobutanone: CASSCF study

Chen

Song

2003

Int J of Quantum Chemistry

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“…1,1,2,2-tetramethyl-3-methylenecyclopropane and 1,l-dimethyl-2-3There are some examples of 1,2-hydrogen shifts leading to en01 isopropylidenecyclopropane (19)) but these could not be isolated. For personal use only.…”

Section: Resultsmentioning

confidence: 99%

Photochemistry of cyclobutanones with nitrogen acids. A potential nucleoside synthesis

Hayes¹,

Jandrisits²,

Lee‐Ruff³

1989

Can. J. Chem.

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“…The photochemical reactions undergone by cyclic ketones have for some time been of widespread interest (2), the principal products being carboxylic acid derivatives (3), enals (2), and cyclic ethers (4,5). Acyl alkyl diradical intermediates (6,7) are commonly invoked and may arise from either the singlet or triplet excited states of the ketone (4,8,9).…”

mentioning

confidence: 99%

“…Acyl alkyl diradical intermediates (6,7) are commonly invoked and may arise from either the singlet or triplet excited states of the ketone (4,8,9).…”

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confidence: 99%

Photochemical Ring Enlargements of Two α-Cyanocycloalkanones

Chip¹,

Lynch²

1974

Can. J. Chem.

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The photochemical transformations undergone by 2-cyano-2-methylcycloheptanone (1) and 2-cyano-2-methylcyclohexanone (2) have been studied in methanol and aqueous dioxane. In the former solvent, 1 is isomerized to three products in the ratio 78:8:13, corresponding to the enals 3a and 3b, and a new ring expansion product 4, respectively. In aqueous dioxane, the cyclic imide 6 was obtained in 18% yield. Cycloalkanone 2 in methanol produces four products in the ratio 61:30:7:1, these being the isomeric enals 8a and 8b, the ester 9, and the ring expansion product 10. No imide related to 6 could be obtained from irradiation of 2 in aqueous dioxane.

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Photochemical ring expansion of cyclic aliphatic ketones. Cyclobutanones and cyclopentanones

Cited by 46 publications

References 13 publications

Photochemical reaction mechanism of cyclobutanone: CASSCF study

Photochemical reaction mechanism of cyclobutanone: CASSCF study

Photochemistry of cyclobutanones with nitrogen acids. A potential nucleoside synthesis

Photochemical Ring Enlargements of Two α-Cyanocycloalkanones

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