Irradiation of methyl diazomalonate in solution. Reactions of singlet and triplet carbenes with carbon-carbon double bonds

Jones, Maitland; Andō, Wataru; Hendrick, Michael E.; Kulczycki, Anthony; Howley, Peter M.; Hummel, Karl F.; Malament, Donald S.

doi:10.1021/ja00776a032

Cited by 89 publications

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“…This would have mimicked the reported photochemical behavior (13), a common occurrence in photochemistry and mass spectroscopy (14). The lack of mimicry here is especially surprising since the n system is fully conjugated.…”

supporting

confidence: 78%

Metal salt catalyzed carbenoids. XVIII. The electron impact mass spectral behavior of diazocarbonyl compounds. I.

Wulfman¹,

Roberts²,

Henderson³

et al. 1984

Can. J. Chem.

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, 554 (1984). Electron impact (EI) mass spectral studies of methyl diazoacetate, ethyl diazoacetate (I), methyl diazoacetoacetate (2). and dimethyl diazomalonate (3) indicate that loss of N2 is exceedingly difficult from the parent ion and was observed only with 3. Diazoacetylacetone exhibits an appreciable (M -28)'. Exact Mass and metastable transitions indicate fragmentation occurs in part via 1,2,3-oxadiazolium ion-radicals (6) or a-lactones (7) There are surprisingly few studies of the mass spectra of diazo compounds (2-12). Frequently the generation of the ion [RCN,]' occurs (presumably the diaza analog of the cyclopropenium ion) (2, 3, 5, 6, 1 1, 12). The reported spectrum of diazomethane (2) exhibited this as a peak of 8.4% intensity and interestingly, possesses an M+ of 96.5%. Paulett and Ettinger (2) also found a value for D(CH2 -H2) of 1.9 eV and for D(CH2 -N2)+, 3.3 eV.Our observation (10) that dimethyl diazomalonate failed to lose N2 to form a (M -28)' ion is somewhat unique since the M+ ion might be expected to readily lose N2 to furnish a carbene-cation-radical stabilized by its substituents. This would have mimicked the reported photochemical behavior (13), a common occurrence in photochemistry and mass spectroscopy (14). The lack of mimicry here is especially surprising since the n system is fully conjugated. Ions possessing the necessary lifetime to pass through a mass spectrometer might be expected to have sufficient time to undergo electronic decay to the most stable cation radicals regardless of which electron had been ejected by electron bombardment. We have now completed a study of the series of structurally related diazo carbonyl compounds, ethyl diazoacetate (I), methyl diazoacetoacetate (2), dimethyl diazomalonate (3), and 3-diazopentane-2,4-dione (4). Their low and medium-high resolution EI mass spectra are tabulated in Tables 1-5. Spectra were obtained at -75, -30, and -13 eV. The experiments were performed using a JEOL-Dl00 double focussing mass spectrometer equipped with a JEOL data system and a JEOL ion defocussing attachment capable of scanning accelerating voltage and thus observing metastable transitions (15). The '~uthor to whom correspondence may be addressed.Undergraduate research participant. IRevision received October 14, 1983.D-100 can be operated in either a low resolution mode or a medium-high resolution mode (up to -10 000 resolution). For the mass ranges and compositions encountered here, it was possible to distinguish between the various elemental compositions for the ions of interest. The inlet system is all glass up to the gap before the ionizing source. Thus, this study was free from the plague of metal catalyzed processes to be expected of diazo compounds and observed in some of the earlier studies in this area (3). Table 6 reveals some of the common fragmentations observed. Table 7 is a listing of all of the nitrogen-containing fragments found in the m s of methyl diazoacetoacetate. Schemes 1-3 reveal the fragmentation sequences obtained by ion defocussing.All ...

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confidence: 78%

Metal salt catalyzed carbenoids. XVIII. The electron impact mass spectral behavior of diazocarbonyl compounds. I.

Wulfman¹,

Roberts²,

Henderson³

et al. 1984

Can. J. Chem.

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“…[103] and related species [106] insert readily into CϪH bonds of the solvent, rather than forming highly strained Wolff products. Owing to the low migratory aptitude of OR, CϪH insertion is often the only reaction of diazoesters 117, with X ϭ H, [107] SiMe 3 , [108] CO 2 R, [64,107,109] COCF 3 , [110] and CONR 2 . [74] Formation of β-lactams, by intramolecular CϪH insertion, is characteristic of diazoamides (see 77, Scheme 15).…”

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confidence: 99%

100 Years of the Wolff Rearrangement

2002

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The conversion of α‐diazo ketones into ketenes, and products derived therefrom, was discovered by Wolff in 1902. Major applications of the Wolff rearrangement, such as the Arndt−Eistert reaction (homologation of carboxylic acids) and the ring contraction of cyclic ketones, have been with us for some while. Nevertheless, substantial progress has been made recently. The reaction mechanism has been explored by means of matrix isolation, time‐resolved spectroscopy, and computation. Full retention of configuration of the migrating group has been established by using enantioselective chromatography. The Arndt−Eistert reaction has witnessed a renaissance in the field of natural products, in particular β‐amino acids and β‐peptides. Ring‐contracting Wolff rearrangements and ketene cycloadditions have been applied in syntheses of increasingly complex, biologically active target molecules. These accomplishments, as well as unsolved problems, are addressed in the present review. (© Wiley‐VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

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“…3 Jones argued that the cyclopropanes obtained by photolysis of methyl diazomalonate derived both from the conventional carbene addition and from cycloaddition of the excited-state of the diazo compound to the alkene, followed by its decomposition to give alkenes of mixed stereochemistry. 2 We thus consider here whether an excited-state of compounds 2-4 might be involved in the cyclohexene insertion product 6. Although spectroscopic study would be ideal, we can make a reasonable argument on the basis of product yields alone.…”

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confidence: 99%

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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Irradiation of methyl diazomalonate in solution. Reactions of singlet and triplet carbenes with carbon-carbon double bonds

Cited by 89 publications

References 3 publications

Metal salt catalyzed carbenoids. XVIII. The electron impact mass spectral behavior of diazocarbonyl compounds. I.

Metal salt catalyzed carbenoids. XVIII. The electron impact mass spectral behavior of diazocarbonyl compounds. I.

100 Years of the Wolff Rearrangement

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

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