Photolysis of N,N-diethyldiazoacetamide. Participation of a noncarbenic process in intramolecular carbon-hydrogen insertion

Tomioka, Hideo; Kitagawa, Hirohisa; Izawa, Yasuji

doi:10.1021/jo01331a023

Cited by 49 publications

(21 citation statements)

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“…1 H NMR of 1a displays one singlet at δ 6.30 (D 2 O:CD 3 CN, 1H, s) for the α–methine proton consistent with a single s-Z configuration deduced from the crystallographic data (SI1) and consistent with several other diazoacetophenones 25,26,27,28,29,30,31 and semi empirical (AM1) and ab initio (HF/6-31G(d)) determinations. 32,33 …”

Section: Resultssupporting

confidence: 67%

2-Diazo-1-(4-hydroxyphenyl)ethanone: a versatile photochemical and synthetic reagent

Senadheera

Evans

Toscano

et al. 2014

Photochem Photobiol Sci

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α-Diazo arylketones are well-known substrates for Wolff rearrangement to phenylacetic acids through a ketene intermediate by either thermal or photochemical activation. Likewise, α-substituted p-hydroxyphenacyl (pHP) esters are substrates for photo-Favorskii rerrangements to phenylacetic acids by a different pathway that purportedly involves a cyclopropanone intermediate. In this paper, we show that the photolysis of a series of α-diazo-p-hydroxyacetophenones and p-hydroxyphenacyl (pHP) α-esters both generate the identical rearranged phenylacetates as major products. Since α-diazo-p-hydroxyacetophenone (1a, pHP N2) contains all the necessary functionalities for either Wolff or Favorskii rearrangement, we were prompted to probe this intriguing mechanistic dichotomy under conditions favorable to the photo-Favorskii reangement, i.e., photolysis in hydroxylic media. An investigation of the mechanism for conversion of 1a to p-hydroxyphenyl acetic acid (4a) using time-resolved infrared (TRIR) spectroscopy clearly demonstrates the formation of a ketene intermediate that is subsequently trapped by solvent or nucleophiles. The photoreaction of 1a is quenched by oxygen and sensitized by triplet sensitizers and the quantum yields for 1a–c range from 0.19 to a robust 0.25. The lifetime of the triplet, determined by Stern-Volmer quenching, is 15 ns with a rate for appearance of 4a of k = 7,1 × 106 s−1 in aq. acetonitrile (1:1 v:v). These studies establish that the primary rearrangement pathway for 1a involves ketene formation in accordance with the photo-Wolff rearrangement. Furthermore we have also demonstrated the synthetic utility of 1a as an esterification and etherification reagent with a variety of substituted α-diazo-p-hydroxyacetophenones, using them as synthons for efficiently coupling it to acids and phenols to produce pHP protect substrates.

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Section: Resultssupporting

confidence: 67%

2-Diazo-1-(4-hydroxyphenyl)ethanone: a versatile photochemical and synthetic reagent

Senadheera

Evans

Toscano

et al. 2014

Photochem Photobiol Sci

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“…[74] Formation of β-lactams, by intramolecular CϪH insertion, is characteristic of diazoamides (see 77, Scheme 15). [70,71,111] c) Stereoselective reaction of singlet carbonyl carbenes with CϭC double bonds was observed only with precursors such as 111, 112, and 117. Rapidly rearranging carbonyl carbenes (R 1 ϭ alkyl or aryl) can add to alkenes from their triplet states, [50] as illustrated by the intramolecular reactivity of 119 (Scheme 19).…”

Section: Competing Reactionsmentioning

confidence: 99%

“…Aside from OϪH insertion with methanol (Ǟ 78), intramolecular CϪH insertion leading to lactams (Ǟ 79 ϩ 80) prevails (Scheme 15). [70,71] As 76 was not obtained in triplet sensitized photolyses, the 1,2-shift of NR 2 is likely to proceed from the excited singlet state of 77. [71] Not surprisingly, 2-diazo-3-oxobutanamides (81) [71b] and 3-diazo-2,4-pyrrolidinediones (83) [72] rearrange by way of alkyl shifts.…”

Section: Migratory Aptitudesmentioning

confidence: 99%

“…[70,71] As 76 was not obtained in triplet sensitized photolyses, the 1,2-shift of NR 2 is likely to proceed from the excited singlet state of 77. [71] Not surprisingly, 2-diazo-3-oxobutanamides (81) [71b] and 3-diazo-2,4-pyrrolidinediones (83) [72] rearrange by way of alkyl shifts. Intramolecular formation of β-lactams [73] and intermolecular insertion, [74] rather than migration of alkoxy and/or amino groups, were observed on photolysis of 82.…”

Section: Migratory Aptitudesmentioning

confidence: 99%

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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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“…to generate nitrogen-free species such as carbenes. Indeed, the observation by Voigt and Meier (20) that photolysis of diazo isatin furnished a diazirine points in the same direction as the observation of a temperature dependence of the photolysis of 3 by Wulfman et al (lo), the observation by Tomioka et al (22) of a non-carbenic path C-H inseration product in the course of the photolysis of the diethylamide of diazoacetic acid, and the observation of a diazoacetylonium ion intermediate in the photolysis of 1 in isopropyl alcohol (23). As noted previously (I), the carbene pathway rationale is extremely attractive but is a house-of-cards.…”

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confidence: 58%

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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Photolysis of N,N-diethyldiazoacetamide. Participation of a noncarbenic process in intramolecular carbon-hydrogen insertion

Cited by 49 publications

References 0 publications

2-Diazo-1-(4-hydroxyphenyl)ethanone: a versatile photochemical and synthetic reagent

2-Diazo-1-(4-hydroxyphenyl)ethanone: a versatile photochemical and synthetic reagent

100 Years of the Wolff Rearrangement

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

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