Chemoselective photochemical surface reaction — Ketene versus carbene reactivity from the photolysis of saturated monolayers of pyridyl diazoesters on single-crystal Pt

Pitters, Jason; Adkinson, Dana K.; Griffiths, K.; Norton, P. R.; Workentin, Mark S.

doi:10.1139/v10-113

Cited by 4 publications

(9 citation statements)

References 24 publications

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“…No significant difference in the N:C ratio is observed despite the complete loss of the isocyanate signal. This suggests that the methylamine reacts with the isocyanate, but may initiate some surface oligimerization (Scheme S1) similar to what we reported for reaction of ketene monolayers with nucleophiles .…”

Section: Resultssupporting

confidence: 79%

“…Most studies have primarily focused on monolayers consisting of long, flexible alkyl chains attached to various surfaces such as organosilanes on silicon (9)(10)(11)(12) or titanium oxide (13,14) and alkanethiols on gold (15)(16)(17)(18). In comparison, there are significantly fewer studies of monolayers consisting of rigid aromatic moieties (19)(20)(21)(22)(23)(24). A popular strategy for modifying the surface properties of SAM is to introduce monolayers with terminal functional groups, and using light or heat to efficiently modify the whole surface simultaneously (25)(26)(27) by exploiting well-established reactions such as the Curtius rearrangement (28)(29)(30)(31).…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…In our previous studies with pyridyl diazoketones and diazoesters, we were able to form remarkably stable, densely packed monolayers on both (111) and (110) Pt surfaces as saturated monolayers in an ultrahigh vacuum (UHV) environment (22)(23)(24). Notably, we reported that the photolysis of 3-and 4-substituted pyridyl diazoketones monolayers generate the corresponding pyridyl ketene via a photo-Wolff rearrangement as a stable monolayer (22). By comparison, 3-and 4-pyridyl diazoacetates showed chemoselectivity; the products observed from the chemistry of the 3-substituted analog arise from the expected carbene intermediate, whereas the 4-substituted pyridyl diazoactetate reacted via the ketene intermediate, which was observed spectroscopically.…”

Section: Introductionmentioning

confidence: 99%

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Photolysis and Thermolysis of Pyridyl Carbonyl Azide Monolayers on Single‐Crystal Platinum

Adkinson

Magri

Pitters

et al. 2013

Photochem & Photobiology

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The photochemical and thermal reactivity of a number of acyl azide-substituted pyridine compounds, namely nicotinyl azide, isonicotinyl azide, picolinyl azide and dinicotinyl azide with investigated as saturated monolayers on a single-crystal Pt(111) surface in an ultrahigh vacuum chamber. Multilayers of the substrates exhibited a maximum rate of desorption at 270 K, above which, stable saturated monolayers formed as characterized by reflection-absorption infrared spectroscopy by observation of C=O and N3 bands at 1700 cm(-1), and 2100 and 1300 cm(-1) respectively. The monolayers were stable up to 400 K. Photolysis of the monolayer (or heating above 400 K) results in the formation of the respective isocyanate intermediate after loss of nitrogen as evidenced by the appearance of a new infrared band at 2260 cm(-1) with concomitant loss of the azide bands. The resulting isocyanate saturated monolayer is stable in absence of nucleophiles, but can be quenched with appropriate nucleophiles.

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Section: Resultssupporting

confidence: 79%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Photolysis and Thermolysis of Pyridyl Carbonyl Azide Monolayers on Single‐Crystal Platinum

Adkinson

Magri

Pitters

et al. 2013

Photochem & Photobiology

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“…15 Application of a pyrid-4-yl alkyl diazoacetate in surface modification processes has already been described. 16 The method reported here may also find use in the synthesis of other new heteroaryl-substituted alkyl diazoacetates.…”

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confidence: 92%

Palladium-Catalyzed Coupling of Pyrid-4-yl Nonaflates with Methyl Diazoacetate

Eidamshaus

Hommes

Reißig

2012

Synlett

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Palladium-catalyzed couplings of pyrid-4-yl nonaflates with methyl diazoacetate are described. After optimization of the reaction conditions the scope of the transformation proved to be fairly broad and a series of pyrid-4-yl-substituted methyl diazoacetates was prepared in generally high yields.Palladium-catalyzed coupling reactions have evolved into one of the most efficient methods for the construction of C-C bonds. 1 Coupling between aryl halides and metalorganic species have been well-established for many years. In contrast, palladium-catalyzed couplings employing CH-active precursors as carbon nucleophiles have only recently been developed. Based on the pioneering work of Hartwig and Buchwald on the intermolecular coupling of enolates derived from ketones, esters and amides, 2 the use of other CH-acidic compounds such as nitriles, nitroalkanes, aldehydes etc. has attracted growing interest in palladium-catalyzed arylation processes over the last years. 3 Recently, two reports have been published describing the use of alkyl diazoacetates as coupling partners: Wang and co-workers developed a protocol for the palladium-catalyzed coupling of vinyl and aryl iodides with ethyl diazoacetate to compounds 2, 4 and Frantz et al. reported the coupling of acceptor-substituted enol triflates 5 providing products such as 4 (Scheme 1).Over the last years we have systematically investigated the behavior of pyrid-4-yl nonaflates in various crosscoupling processes. 6 Intrigued by the reports of the two groups mentioned above, we wanted to identify reaction conditions for palladium-catalyzed couplings of pyrid-4-yl nonaflates with alkyl diazoacetates, which should lead to structurally interesting new pyrid-4-yl diazoacetates. Only a few reports describe the preparation and use of pyridyl diazoacetates, and the majority of the synthetic routes are based on diazo group transfer processes employing pyrid-4-yl acetates as starting materials. 7 Hence, the palladium-catalyzed coupling between pyrid-4-yl nonaflates and alkyl diazoacetates would present a useful and flexible alternative to access these versatile compounds.As we demonstrated earlier, pyrid-4-yl nonaflates 11 can be prepared through a simple two-step process utilizing a TMSOTf-promoted cyclocondensation of β-ketoenamides 10 followed by a nonaflation step with the intermediate 4-hydroxypyridines (Scheme 2). 8 Two routes have been developed for the preparation of the required β-ketoenamides: a multi-component approach based on the reaction of lithiated alkoxyallenes 5, nitriles 6, and carboxylic acids 7 (Scheme 2, route A) 9 or the acylation of simple enaminoketones 8 with acyl chlorides 9 (route B). 10 In addition to a series of highly substituted pyridine derivatives, we also prepared enantiopure pyridine derivatives with side chains bearing stereogenic centers in the 2-and/or 6-position. 11 Some of these new pyridines proved to be good ligands for asymmetric transformations, including the addition of zinc organyls to aldehydes or the iridium-catalyzed hydrogenation of...

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Ester-Carbene and Its Dimerization with Exclusive Cis-Selectivity on a Silver Surface

Chu

Chou

et al. 2022

J. Phys. Chem. C

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Diazo compounds are key precursors to carbenes. Here, methyl diazoacetate is dosed onto an Ag(111) surface and subjected to 365 nm UV light activation. Loss of N2 generates a metastable metal-bonded methyl ester-carbene at 100 K, which is confidently diagnosed using reflection–absorption infrared spectroscopy in conjunction with the theoretically calculated frequencies, intensities, and normal modes, corroborating the structure assignments. To the best of our knowledge, this is the first synthesis of extended surface-based ester-carbene and its capture. Upon annealing the surface at 200 K, part of the neighboring ester-carbene species are well positioned to undergo intraoverlayer dimerization and afford preferentially cis-configured alkene (maleate). We thus demonstrate the efficient formation of thermodynamically less stable, isomerically pure cis-alkenes via a surface-mediated process. In addition to dimerization, heating Ag(111) to 200 K induces selective C–O bond cleavage of the methyl ester-carbene to yield methoxy and ketenyl fragments, which eventually yield formaldehyde, methanol, and ketene as gas-phase products above 300 K. In contrast, no trace Wolff rearrangement, the reaction characteristic of diazo carbonyl compounds, is observed. Remarkable stereoselectivity and chemoselectivity are demonstrated, and this work showcases how a silver surface can act to accommodate carbenes and allows the characterization of reactive intermediates usually seen only in matrices.

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Chemoselective photochemical surface reaction — Ketene versus carbene reactivity from the photolysis of saturated monolayers of pyridyl diazoesters on single-crystal Pt

Cited by 4 publications

References 24 publications

Photolysis and Thermolysis of Pyridyl Carbonyl Azide Monolayers on Single‐Crystal Platinum

Photolysis and Thermolysis of Pyridyl Carbonyl Azide Monolayers on Single‐Crystal Platinum

Palladium-Catalyzed Coupling of Pyrid-4-yl Nonaflates with Methyl Diazoacetate

Ester-Carbene and Its Dimerization with Exclusive Cis-Selectivity on a Silver Surface

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