Photochemistry of dispiro-1,3-cyclobutanediones in methylene chloride and methanol solutions

Krapcho, A. Paul; Abegaz, Berhanu M.

doi:10.1021/jo00929a026

Cited by 8 publications

(6 citation statements)

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“…[52] Compounds 1a and 1b have relatively low quantum yields between 0.03-0.04. In agreement with previous reports, the cyclohexyl diones 1c, [46,47] and 1d, undergo efficient photoreaction, with quantum yield of decarbonylations of 0.34 and 0.33, respectively (Table 1).…”

Section: Resultssupporting

confidence: 92%

“…[49] Previous work by Krapcho reported that photolysis of cyclobutanediones 1a-1c in dichloromethane undergo either a formal reverse [2+2] cycloaddition to generate the ketenes 2a-c, or two sequential decarbonylations to form alkenes 4a-4c via the corresponding cyclopropanones 3a-3c. [47] In agreement with Krapcho's previous studies, diones 1a-c undergo efficient photoreaction upon irradiation at 312nm in dichloromethane (DCM). The photochemical reactions were monitored by gas chromatography.…”

Section: Resultssupporting

confidence: 90%

“…Spirocyclobutanediones 1a-d were chosen as photochemical precursors for singlet state Norrish Type I decarbonylation in crystals because it has been reported that most undergo decarbonylation upon irradiation at either 254 or 312nm in solution [46] (Scheme 1), and all have relatively high melting points (> 75 C). [47] Spirocyclobutanediones 1a-d differ by the size of the side rings (1a-1d), as well as by the substitution patterns (1c and 1d). For the remainder of the manuscript, compounds 1a-d will be referred by the size of the side ring (i.e., cyclobutyl 1a, cyclopentyl 1b, cyclohexyl 1c, and t-butylcyclohexyl 1d).…”

Section: Resultsmentioning

confidence: 99%

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Ring strain release as a strategy to enable the singlet state photodecarbonylation of crystalline 1,4‐cyclobutanediones

Kuzmanich

2011

J of Physical Organic Chem

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Challenging most chemists' intuition, highly reactive dialkyl biradicals can be reliably generated in the solid state by taking advantage of the photodecarbonylation of cyclic ketones. However, it has been shown that radical stabilizing groups with resonance‐delocalizing abilities at the α‐carbons of the precursor are required to facilitate the α‐cleavage reaction, and that triplet state reactivity is essential to slow down the combination of the intermediate acyl–alkyl biradical back to the starting ketone. Relatively long triplet acyl–alkyl biradical lifetimes give a chance for the loss of CO to occur. Looking for additional strategies to generate transient biradicals in solids, we studied the solid state photochemistry of four aliphatic, dispiro‐substituted 1,4‐cyclobutandiones (1a–d) that were expected to react from the singlet state. We hypothesized that the release of ring strain from the small ring carbonyl would make the reverse acyl–alkyl combination disfavored, allowing for the loss of CO to occur efficiently and irreversibly. We report here the results of studies carried out in solution, bulk (powder) crystals, and nanocrystalline photochemistry. We have recently shown that excitation of dispirocyclohexyl‐1,3‐cyclobutanedione 1c led to the trapping of the intermediate oxyallyl with a half life of about 42 min. Our studies with the three other crystalline derivatives revealed that, while all react efficiently, the remarkably long lifetime of oxyallyl is unique to crystals of 1c. Copyright © 2011 John Wiley & Sons, Ltd.

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Section: Resultssupporting

confidence: 92%

Section: Resultssupporting

confidence: 90%

Section: Resultsmentioning

confidence: 99%

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Ring strain release as a strategy to enable the singlet state photodecarbonylation of crystalline 1,4‐cyclobutanediones

Kuzmanich

2011

J of Physical Organic Chem

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“…Other examples of reaction-enabling substituents that support the generality of the solid-state reaction include the a,a-dialkoxy groups of bisketal 181, which has an aromatic p-system out of alignment to stabilize the radical intermediates (Scheme 2.44) [76]. The spiro-cyclobutanone 183 [77] and diphenyl cyclopropenone 185 [78] serve to illustrate an alternative strategy to enable the solid-state reaction based on the release of strain energy. Compound 183 reacts by a double decarbonylation process to give bis-cyclohexylidene 184, and cyclopropenone 185 reacts with an unprecedented quantum chain transformation to generate diphenylacetylene 186.…”

Section: Reactivity and Stabilitymentioning

confidence: 99%

CarbonCarbon Bond Formation by the Photoelimination of Small Molecules in Solution and in Crystals

Shiraki

2009

Handbook of Synthetic Photochemistry

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The formation of CÀC bonds is arguably the most important reaction in organic synthesis. While many strategies have been developed to link organic fragments with a wide range of thermal processes, photochemical syntheses based on the elimination of a small molecule, X (Scheme 2.1), offer significant advantages when the desired structures are highly strained or hindered. In this chapter, we will describe examples of the generation of CÀC bonds through the photoinduced extrusion of small molecules such as N 2 , CO 2 , CO, and SO 2 , as well as the formal extrusion of S atoms. After describing the most general mechanistic aspects covering these reactions and the current scope and limitations, we will illustrate examples involving these reactions in solution. Following that, we will describe a strategy based on the use of crystalline solids that helps to control the fate of the reaction intermediates. Finally, we will illustrate the use of crystalline ketones (X¼CO) as one of the most promising general methods for the synthesis of compounds with all-carbon adjacent stereogenic quaternary centers.The photoelimination of a small stable molecule X accompanied by the formation of a new CÀC bond could, in principle, take place in a concerted manner through cyclic transition states with simultaneous bond-breaking and bond-making steps that follow trajectories determined by orbital symmetry considerations. However, as it pertains to photodecarbonylation reactions, theoretical analysis on the formation of hydrogen and CO from formaldehyde suggests that the concerted process is significantly less likely than the stepwise cleavage of the HÀC(O)ÀH bonds [1]. Similar conclusions have been made for the elimination of N 2 and H 2 from simple diazene (HN¼NH) [2]. In fact, evidence for concerted reactions is available only in a handful of cases (vide infra). Most examples involve a four-step process that starts with electronic excitation (step 1) and is followed by an a-cleavage reaction (step 2) to give a primary biradical or radical pair (BR-1). Subsequent dissociation of the small molecule X (step 3) results in the formation of the secondary biradical or radical pair (BR-2), which is followed by radical-radical combination to give the desired product (step 4).Handbook of Synthetic Photochemistry. Edited

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“…6), except that 25a exclusively rearranged to the thermally and photochemically sensitive enol 13-lactone 29a. 40 Irradiation of 25 in methanol in Pyrex vessels afforded a rather complex spectrum of products ( Fig. 11).…”

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Photolysis of Saturated Four‐Membered Rings with Two Exocyclic Double Bonds: A Photoextrusion Route to (Hetero)Methylenecyclopropanes

Quast

Fuss

1982

Israel Journal of Chemistry

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Photochemistry of dispiro-1,3-cyclobutanediones in methylene chloride and methanol solutions

Cited by 8 publications

References 7 publications

Ring strain release as a strategy to enable the singlet state photodecarbonylation of crystalline 1,4‐cyclobutanediones

Ring strain release as a strategy to enable the singlet state photodecarbonylation of crystalline 1,4‐cyclobutanediones

CarbonCarbon Bond Formation by the Photoelimination of Small Molecules in Solution and in Crystals

Photolysis of Saturated Four‐Membered Rings with Two Exocyclic Double Bonds: A Photoextrusion Route to (Hetero)Methylenecyclopropanes

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