Ultrafast time‐resolved studies of the photochemistry of diazo carbonyl compounds

Burdziński, Gotard; Platz, Matthew S.

doi:10.1002/poc.1601

Cited by 40 publications

(86 citation statements)

References 28 publications

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“…However with the development of ultrafast flash photolysis, new evidences pointing in other directions have been brought to light. 45 The time-resolved UV-vis and IR spectroscopic studies of BpCN 2 COMe 46 35 and BpCOCN 2 Me 47 confirmed that the concerted and stepwise pathways contributed with similar quantum yields to the ketene formation. If a carbene is formed, it can exist in the triplet or singlet state and its population will depend on the energies of each level.…”

Section: Concerted and Stepwise Pathwayssupporting

confidence: 50%

3.19 The Wolff Rearrangement

Candeias

Trindade

Góis

et al. 2014

Comprehensive Organic Synthesis II

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Section: Concerted and Stepwise Pathwayssupporting

confidence: 50%

3.19 The Wolff Rearrangement

Candeias

Trindade

Góis

et al. 2014

Comprehensive Organic Synthesis II

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“…1 Both proceed by elimination reactions coupled with a 1,2-carbon migration before reacting with a nucleophilic trapping reagent that, overall, converts an α-substituted ketone to a carboxylic acid. Photochemical versions of these rearrangements, the photo-Wolff (pWR) 2 and photo-Favorskii (pFR) 3 rearrangements, are well-known variations of these rearrangements (Scheme 1). Of these two, the photo-Favorskii rearrangement is the more recent 3,4 and less well-studied.…”

Section: Introductionmentioning

confidence: 99%

“…8 These similarities plus recent mechanism studies of the photo-Favorskii reaction 3c,7b,9,10 have added significantly to our understanding of the rearrangement reaction, inviting a more in depth comparison between the pFR and the more well-established pWR. 2,11 …”

Section: Introductionmentioning

confidence: 99%

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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“…It has been demonstrated 22,23 that in some cases a branched mechanism is possible: the ketene is formed in both a fast process (t < 0.4 ps) from the diazoketone excited state (concerted Wolff rearrangement) and a slower process (700 ps) from the relaxed singlet ketocarbene. The ketene was detected for structurally similar molecules by Delaire et al 24 using UV-vis laser photolysis techniques and by Scaiano et al using IR detection.…”

Section: Quantum Yield Determinationsmentioning

confidence: 99%

Effects of solvent, excitation wavelength, and concentration on the photobehavior of some diazonaphthoquinones

Cipolloni¹,

Gentili²,

Ortica³

et al. 2011

Arkivoc

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Diazonaphthoquinones (DNQs) are the photoactive components of resists used in the fabrication of integrated circuits. Exposed to radiation these compounds release molecular nitrogen undergoing a ring contraction (Wolff rearrangement). In this work the photobehavior of three compounds bearing two and three chromophoric DNQ units has been studied. Photochemical quantum efficiencies of reactant disappearance have been determined in acetonitrile at 290 K and in ethanol/methanol (4/1, v/v) solid matrix at 80 K, using some irradiation wavelengths and different DNQ concentrations. The results obtained show that the course of the photoreaction strongly depends on the medium, the concentration, the temperature and the excitation wavelength.

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Ultrafast time‐resolved studies of the photochemistry of diazo carbonyl compounds

Cited by 40 publications

References 28 publications

3.19 The Wolff Rearrangement

3.19 The Wolff Rearrangement

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

Effects of solvent, excitation wavelength, and concentration on the photobehavior of some diazonaphthoquinones

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