Selective photooxidation of ortho-substituted benzyl alcohols and the catalytic role of ortho-methoxybenzaldehyde

Scandura, Gabriele; Palmisano, Giovanni; Yurdakal, Sedat; Tek, Bilge Sina; Özcan, Levent; Loddo, Vittorio; Augugliaro, Vincenzo

doi:10.1016/j.jphotochem.2016.05.022

Cited by 8 publications

(7 citation statements)

References 29 publications

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“…In 2016, the Augugliaro group reported the photocatalytic effect of orthomethoxybenzaldehyde, produced by oxidation of ortho-methoxybenzyl alcohol over TiO2 photocatalysts, on homogeneous photooxidation of other alcohols under UV light. 19 Surprisingly, this important finding that should have alarmed many researchers has been sadly neglected by the community, as this paper has received only few citations so far. Two years later, Pavan et al addressed the question of benzyl alcohol self-oxidation under UV-light.…”

Section: Introductionmentioning

confidence: 95%

Benzaldehyde-Promoted (Auto)Photocatalysis under Visible Light: Pitfalls and Opportunities in Photocatalytic H2O2 Production

Krivtsov

Vazirani²,

Mitoraj³

et al. 2022

Preprint

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Selective photooxidation of aromatic alcohols to corresponding aldehydes is a widely used model reaction for evaluation of performance of heterogeneous photocatalysts. A chief example is the photocatalytic production of hydrogen peroxide via reduction of dioxygen with concomitant photooxidation of benzyl alcohol to benzaldehyde. Although it has long been known that photoexcitation of benzaldehyde under UV light yields reactive benzaldehyde radicals capable of oxidizing substrates such as benzyl alcohol, it was assumed that such autocatalytic processes cannot be initiated under visible light irradiation. Herein we demonstrate the ability of benzaldehyde to promote auto-photocatalytic oxidation of benzyl alcohol and produce large quantities of H2O2 in solvent-free (no water) or biphasic (with water) systems even under nominally solar-simulated visible light (>420 nm cutoff filter) irradiation. While these results open up broader prospects for the use of benzaldehyde in visible light-driven photocatalysis as exemplified by the ability of benzaldehyde to photocatalyze H2O2 production even in the presence of alternative electron donors (e.g., ethanol), they also shed some critical light on the plethora of research reports on photocatalytic H2O2 production in which benzyl alcohol was employed as electron donor. Since the autocatalytic pathway based on the photocatalytic activity of benzaldehyde formed during photocatalysis under such conditions cannot be neglected, the interpretations of photocatalytic performance are likely contentious and distorted in such reports. We conclude that the use of benzyl alcohol as a model electron donor in photocatalytic studies should be definitely discouraged, and highlight the importance of carrying out simple check protocols for excluding similar issues when using alternative substrates.

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Section: Introductionmentioning

confidence: 95%

Benzaldehyde-Promoted (Auto)Photocatalysis under Visible Light: Pitfalls and Opportunities in Photocatalytic H2O2 Production

Krivtsov

Vazirani²,

Mitoraj³

et al. 2022

Preprint

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“…The radical cations perform the C-H bond functionalization task. Recently, by consistently fine-tuning the TiO2 photocatalysts, especially for visible-light excitation and reaction parameter optimization, the following delicate examples of challenging organic synthesis photocatalyzed by TiO2 have appeared: aerobic oxidation of alcohol to aldehydes [31,35,37,51,[59][60][61][62][63][64][65][66][67][68][69], aerobic oxidative condensation of benzylamines to imines [30,36,49,70], olefin epoxidation [71,72], C-H arylation with aryl diazonium compounds [73,74], desilylative Michael addition between benzyltrimethylsilane and electron-poor olefins [75][76][77][78], pyridine anti-Markovnikoff addition to diphenylethlyene [38], 4-aryltetralone synthesis by styrene [2 + 2 + 2] cyclo-addition [79,80], and amine alkylation with alcohol as an alkylating reagent [81][82][83][84][85]. These reports successfully fulfilled the organic transformations with high yield, excellent selectivity, mild conditions, and wide substrate scope.…”

Section: Introductionmentioning

confidence: 99%

TiO2 Photocatalyzed C–H Bond Transformation for C–C Coupling Reactions

Wang

Liu

et al. 2018

Catalysts

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Fulfilling the direct inert C–H bond functionalization of raw materials that are earth-abundant and commercially available for the synthesis of diverse targeted organic compounds is very desirable and its implementation would mean a great reduction of the synthetic steps required for substrate prefunctionalization such as halogenation, borylation, and metalation. Successful C–H bond functionalization mainly resorts to homogeneous transition-metal catalysis, albeit sometimes suffering from poor catalyst reusability, nontrivial separation, and severe biotoxicity. TiO2 photocatalysis displays multifaceted advantages, such as strong oxidizing ability, high chemical stability and photostability, excellent reusability, and low biotoxicity. The chemical reactions started and delivered by TiO2 photocatalysts are well known to be widely used in photocatalytic water-splitting, organic pollutant degradation, and dye-sensitized solar cells. Recently, TiO2 photocatalysis has been demonstrated to possess the unanticipated ability to trigger the transformation of inert C–H bonds for C–C, C–N, C–O, and C–X bond formation under ultraviolet light, sunlight, and even visible-light irradiation at room temperature. A few important organic products, traditionally synthesized in harsh reaction conditions and with specially functionalized group substrates, are continuously reported to be realized by TiO2 photocatalysis with simple starting materials under very mild conditions. This prominent advantage—the capability of utilizing cheap and readily available compounds for highly selective synthesis without prefunctionalized reactants such as organic halides, boronates, silanes, etc.—is attributed to the overwhelmingly powerful photo-induced hole reactivity of TiO2 photocatalysis, which does not require an elevated reaction temperature as in conventional transition-metal catalysis. Such a reaction mechanism, under typically mild conditions, is apparently different from traditional transition-metal catalysis and beyond our insights into the driving forces that transform the C–H bond for C–C bond coupling reactions. This review gives a summary of the recent progress of TiO2 photocatalytic C–H bond activation for C–C coupling reactions and discusses some model examples, especially under visible-light irradiation.

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“…Methoxybenzyl alcohols occur naturally in trace amounts in specific species of fungi and are produced industrially. Like the chlorinated benzyl alcohols in the present study, 4METBZOH and 3,4METBZOH have limited industrial applications, and are primarily used as precursors for production of aromatic aldehydes (Higashimoto et al, 2009;Morad et al, 2017;Scandura et al, 2016). To the best of the author's knowledge, none of the benzyl alcohols contained in the present study has ever been reported as constituent of any oil reservoir fluids.…”

Section: Benzyl Alcoholsmentioning

confidence: 72%

“…Chlorinated, methoxy and hydroxyl benzyl alcohols are not used in large scale industrial operations. Hydroxy, methoxy and chlorobenzyl alcohols are used in small industrial scale as precursors for production of aromatic aldehydes, as model compounds to study the oxidation of substituted benzyl alcohols, and to evaluate the performance of selective catalyzed processes aiming for production of aromatic aldehydes (Esteruelas et al, 2011;Higashimoto et al, 2009;Morad et al, 2017;Scandura et al, 2016). 4-Chlorobenzyl alcohols have also been reported to be used as reagent and to assess catalysts for the Friedel-Crafts alkylation of aromatic hydrocarbons (Mantri et al, 2005).…”

Section: Benzyl Alcoholsmentioning

confidence: 99%

Development of new oil/water partitioning tracers for the determination of residual oil saturation in the inter-well region of water-flooded reservoirs

Silva¹

2021

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is credited to have said "the value of achievement lies in the achieving." This is true for everything in life, and I feel very lucky and thankful for all the people I worked with in the path leading to this thesis. It is also their achievement, as it would not be possible without them. I learned and was trained by the best in the field, who also showed me that an open-mind, humility, and hard-work pave the way forward. I would like to thank my supervisors, Professor Tor Bjørnstad and Professor Svein Magne Skjaeveland. Thank you, Tor, for all the insights, trust, freedom, patience, and advice! You truly are a role model, and I will be happy if I become half of what you are, both as a researcher and as a person. I could not have done this without you! Thank you Svein for all the kind and motivating words, for the example, and for the rigor with flexibility. This would not happen without you! I want to thank the team of the "Tracer Technology department" at IFE, particularly Sissel Opsahl Viig for sharing her knowledge, time, patience, and good humour, as well as for the help in disassembling and assembling instrumentation! Per Arne Hubred, one of the best humoured and cleverest engineers I ever met, who made the "magic happen" whenever experimental needs would hit a wall. Are Haugen, for all the trouble and help in welcoming me to a new workplace and a new country. Laura Ferrando-Climent, for all the small talk in coffee breaks, confidences, incentive, the friendship, and the sharing of insights about good scientific work. A special thank you to Helge Stray, my office colleague, "informal supervisor", for all the fruitful discussions and exchange of ideas, reviews, motivation, friendship, and help with personal and logistic issues upon my arrival in Norway. I would also like to thank the National IOR Centre of Norway for employing me and all its fantastic members, past and present colleagues at UiS, IFE and NORSE, especially Mahmoud Ould Metidji for the fantastic comradeship, friendship, and collaboration, Thomas Brichart vi for introducing me to the "nano-world" and for the comradeship, Jaspreet Singh Sachdeva for the optimism, motivation, and the insights about pore-scale phenomena, Eystein Opsahl for the warmth, good humour, good discussions, and excellent collaboration. Additionally, I want to thank Aksel Hiorth, Jan Ludvig Vinningland, Merete Madla Vadland, Randi Valestrand, for all the gatherings, discussions, and insights always with lots of fun! Many more are left out, each with valuable contributions. Working with the National IOR Centre of Norway was an exciting and challenging experience, filled with excellent scientific discussions, exchange of ideas and fun, without forgetting our industry partners and their valuable input. Finally, my biggest thank you to my family! To Sofia, for the strength and constant support throughout all the challenges I faced even while facing her own! None of my achievements would be possible without you as my partner and inspiration! To Maria João and Francisca, for being t...

show abstract

Selective photooxidation of ortho-substituted benzyl alcohols and the catalytic role of ortho-methoxybenzaldehyde

Cited by 8 publications

References 29 publications

Benzaldehyde-Promoted (Auto)Photocatalysis under Visible Light: Pitfalls and Opportunities in Photocatalytic H2O2 Production

Benzaldehyde-Promoted (Auto)Photocatalysis under Visible Light: Pitfalls and Opportunities in Photocatalytic H2O2 Production

TiO2 Photocatalyzed C–H Bond Transformation for C–C Coupling Reactions

Development of new oil/water partitioning tracers for the determination of residual oil saturation in the inter-well region of water-flooded reservoirs

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