Photochemical transformations.  XLIX.  Benzpropiolactone

Chapman, O. L.; McIntosh, C. L.; Pacansky, J.; Calder, G. V.; Orr, G F

doi:10.1021/ja00793a046

Cited by 52 publications

(23 citation statements)

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“…Vibrational spectra are simulated using the B3LYP/6-31G(d) level of theory 41 and scaled by 0.9614 to correct for anharmonicity. The CASSCF (8,8) Additional IR and NMR spectra (Figures S1−S12) and calculated structures of carbene 18 ( Figure S13). Absolute energies and Cartesian coordinates for all calculated compounds and imaginary frequencies for transition states.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

Ketene–Ketene Interconversion. 6-Carbonylcyclohexa-2,4-dienone–Hepta-1,2,4,6-tetraene-1,7-dione–6-Oxocyclohexa-2,4-dienylidene and Wolff Rearrangement to Fulven-6-one

2014

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6-Carbonylcyclohexa-2,4-dienone (1) has been generated by flash vacuum thermolysis (FVT) with Ar-matrix isolation of methyl salicylate (7), 2-phenylbenzo-1,3-dioxan-4-one (8), phthalic peranhydride (9), and benzofuran-2,3-dione (11) and also by matrix photolysis of 9, 11, and 2-diazocyclohepta-4,6-dien-1,3-dione (12). In each case, FVT above 600 °C results in decarbonylation of 1 and Wolff rearrangement to fulven-6-one (13) either concertedly or via open-shell singlet 6-oxocyclohexa-2,4-dienylidene (18). Ketenes 1 and 13 were characterized by IR spectroscopy. Photolysis of matrix-isolated 1 at 254 nm also results in the slow formation of 13. The sequential formation of ketenes 1 and 13 from 7 has also been monitored by FVT-mass spectrometry, and 13 has been trapped with MeOH to afford methyl 1,3-cyclopentadiene-1- and -2-carboxylates 15 and 16. FVT of methyl salicylate-1-(13)C 7a revealed a deep-seated rearrangement of the (13)C-labeled 1a to hepta-1,2,4,6-tetraen-1,7-dione (17a) by means of electrocyclic ring opening followed by a facile 1,5-H shift and recyclization prior to CO-elimination and ring contraction to (13)C-labeled 13. The rearrangement mechanism is supported by M06-2X/6-311++G(d,p) calculations, which predict feasible barriers for the FVT rearrangements and confirm the observed labeling pattern in the isolated methyl salicylate 7a/7b and methyl cyclopentadienecarboxylates 20 and 21 resulting from trapping of 13 with MeOH.

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Section: ■ Experimental Sectionmentioning

confidence: 99%

Ketene–Ketene Interconversion. 6-Carbonylcyclohexa-2,4-dienone–Hepta-1,2,4,6-tetraene-1,7-dione–6-Oxocyclohexa-2,4-dienylidene and Wolff Rearrangement to Fulven-6-one

2014

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“…Some examples to illustrate this application include the syntheses of cyclobutadiene 3 by sequential cyclization of pyranone 1, followed by photodecarboxylation of bicyclic lactone 2 reported by Cram [5], the preparation of benzyne 5 by the photodecarbonylation of benzocyclobutanone 4 [6] or by the double decarboxylation of diacyl peroxide 6 [7,8], and the synthesis of benzocyclopropane 9 by the denitrogenation of indazole 8 (Scheme 2.3) [9]. Because of the intrinsic instability of these structures, reactions of this type must be carried out in low temperature matrices for the spectroscopic characterization of the products by UV-Vis and IR methods.…”

Section: Synthesis Of Unstable Moleculesmentioning

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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“…However, the photochemical equilibrium between the ketoketene and the isomeric lactone has been detected using IR (Ar matrix) spectroscopy. 4 α-Thiocarbonylthioketenes have hitherto been a poorly known class of compounds. Only a few noncyclic examples of such compounds have been described.…”

Section: Methodsmentioning

confidence: 99%

Flash Vacuum Thermolysis of 4H-3,1-Benzodithiin-4-thione: UV-Photoelectron Spectroscopy Characterization of Benzothiet-2-thione and Quantum Chemistry Studies

Drewnowski

Leśniak

Chrostowska³

et al. 2009

Phosphorus, Sulfur, and Silicon and the Related Elements

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Photochemical transformations. XLIX. Benzpropiolactone

Cited by 52 publications

References 0 publications

Ketene–Ketene Interconversion. 6-Carbonylcyclohexa-2,4-dienone–Hepta-1,2,4,6-tetraene-1,7-dione–6-Oxocyclohexa-2,4-dienylidene and Wolff Rearrangement to Fulven-6-one

Ketene–Ketene Interconversion. 6-Carbonylcyclohexa-2,4-dienone–Hepta-1,2,4,6-tetraene-1,7-dione–6-Oxocyclohexa-2,4-dienylidene and Wolff Rearrangement to Fulven-6-one

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

Flash Vacuum Thermolysis of 4H-3,1-Benzodithiin-4-thione: UV-Photoelectron Spectroscopy Characterization of Benzothiet-2-thione and Quantum Chemistry Studies

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