1,2-Hydrogen migration and alkene formation in the photoexcited states of alkylphenyldiazomethanes

Celebi, S.; Leyva, Soccoro; Modarelli, David A.; Platz, Matthew S.

doi:10.1021/ja00072a014

Cited by 61 publications

(53 citation statements)

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“…Such 1,2-shifts have been demonstrated repeatedly for nitrogenous carbene precursors that are subject to 1,2 hydrogen shifts or carbon shifts to relieve ring strain. [4][5][6][7][8][9][10] We 11-13 and others [14][15][16][17][18] have shown in previous work that photolysis of dibenzothiophene-S-oxide and its derivatives leads to chemistry that appears to derive from S-O cleavage and formation of atomic oxygen. Although direct evidence for this mechanism in the form of spectroscopic detection of O( 3 P) is lacking, we have recently shown through time-resolved IR experiments that benzoyl nitrene is formed on photolysis of N-benzoyl dibenzothiophene sulfilimine.…”

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confidence: 96%

S,C-Sulfonium Ylides from Thiophenes: Potential Carbene Precursors

2007

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Carbenes remain important and intriguing reactive intermediates in organic chemistry despite years of study for many reasons, among them the access they provide to unusual product compounds, their differing chemistry depending on spin state, and their mechanistic complexity. Photochemical precursors to carbenes, such as diazo compounds and diazirines, are often favored, because they can yield carbenes by photolysis at low temperatures and can be used for laser flash photolysis experiments. However, because these nitrogenous precursors have been shown to undergo reactions in their excited states that mimic chemistry expected from the carbene itself, there is demand for alternative practical precursors. In this Communication, we report the use of S,C-sulfonium ylides 1-4 as photochemical carbene precursors, as illustrated in Scheme 1 for compound 4.The choice of compounds 1-4 as potential precursors to dicarbomethoxycarbene for this study was driven by two considerations. First S,C-ylides of malonates are known to be stable and easy to prepare, at least in part because of the electron withdrawing groups that delocalize the formal negative charge. Second, by generating dicarbomethoxycarbene 1-3 for the proof-of-concept work of showing carbene generation, we believed we could distinguish between reactions of the carbene and a potential excited state Wolfflike rearrangement that might yield a ketene derivative. Such 1,2shifts have been demonstrated repeatedly for nitrogenous carbene precursors that are subject to 1,2 hydrogen shifts or carbon shifts to relieve ring strain. [4][5][6][7][8][9][10]

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confidence: 96%

S,C-Sulfonium Ylides from Thiophenes: Potential Carbene Precursors

2007

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“…They are often generated as short-lived reaction intermediates during the thermolysis/photolysis of nitrogenous precursors, [3] such as diazo compounds [4] and 3H-diazirines, [5] which sometimes undergo rearrangement in the excited state (RIES), circumventing carbene intermediacy. [6][7][8] Despite their electron-deficient character, carbenes can also act as Brønsted-Lowry bases. Carbenium ions may be formed by protonation of carbenes (Scheme 1), [9][10][11] but also by protonation of diazo compounds [12] and 3H-diazirines.…”

Section: Carbenesmentioning

confidence: 99%

“…Buckminsterfullerene [(C 60 -I h ) [5,6]fullerene] has 60 identical carbon atoms that are bonded to each other in the shape of a truncated icosahedron, cf. a soccer ball, in which a carbon atom occupies each vertex ( Figure 7a).…”

Section: Fullerenesmentioning

confidence: 99%

“…[86] Recently, the precise role of H-ZSM-5 in this conversion has been questioned. [87] The formation of the CH 2 @(C 70 -D 5h (6) ) [5,6]fullerene IC by the Krätschmer-Huffman method was recently communicated, [88] although not independently confirmed. The putative fullerene IC was isolated in Ͼ90 % purity by HPLC and characterized by ESR and IR spectroscopy.…”

Section: Methylenementioning

confidence: 99%

“…The putative fullerene IC was isolated in Ͼ90 % purity by HPLC and characterized by ESR and IR spectroscopy. To rule out the formation of an exohedral fullerene, such as 3ЈH-cyclopropa [ (6) ) [5,6]fullerene by an innermolecular reaction of CH 2 with the concave endohedral surface of the fullerene cage is expected to be slow as a result of poor orbital overlap.…”

Section: Methylenementioning

confidence: 99%

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Constrained Carbenes

Rosenberg

Brinker

2006

Eur J Org Chem

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Carbenes traditionally have been used for cyclopropane synthesis but little else, since their reactions are difficult to control. However, the burgeoning discipline of supramolecular carbene chemistry—reactions in which highly reactive, divalent carbon intermediates are generated within the confines of host compounds—is making steady progress towards solving this problem. Various carbenes generated within cyclodextrins, hemicarcerands, and zeolites demonstrate increased selectivities and lifetimes since their usual decay pathways are blocked. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

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Photochemical Hydrogen Migration in Methylanthronylidenes

Wandel¹,

Sander²

1999

Eur. J. Org. Chem.

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The photochemistry of 4‐methyl‐9,10‐diazoanthrone (7a) and 1,4‐dimethyl‐9,10‐diazoanthrone (7b) was investigated in argon matrices at 10 K. Visible‐light irradiation results in the formation of the anthronylidenes 5a and b, respectively, which were identified by oxygen trapping, by comparison of the IR and UV/Vis spectra with that of the parent anthronylidene 6, and by comparison of the IR spectrum with that calculated by DFT methods. The carbenes 5 are thermally stable under the conditions of matrix isolation; however, irradiation with visible or UV light results in the rearrangement to the quinone methides 10a and b.

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1,2-Hydrogen migration and alkene formation in the photoexcited states of alkylphenyldiazomethanes

Cited by 61 publications

References 0 publications

S,C-Sulfonium Ylides from Thiophenes: Potential Carbene Precursors

S,C-Sulfonium Ylides from Thiophenes: Potential Carbene Precursors

Constrained Carbenes

Photochemical Hydrogen Migration in Methylanthronylidenes

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