Brønsted Acid Catalyzed Morita–Baylis–Hillman Reaction: A New Mechanistic View for Thioureas Revealed by ESI‐MS(/MS) Monitoring and DFT Calculations

Amarante, Giovanni W.; Benassi, Mario; Milagre, Humberto M. S.; Braga, Ataualpa Albert Carmo; Maseras, Feliu; Eberlin, Marcos N.; Coelho, Fernando

doi:10.1002/chem.200900966

Cited by 74 publications

(21 citation statements)

References 197 publications

(54 reference statements)

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“…To the best of our knowledge, most on-line ESI MS approaches sampled reaction solution at a pressure near atmospheric or higher, where the solution was delivered to ESI by gravity or positive gas pressure [45][46][47][48][49][50][51]. However, our reaction system needs to be maintained at a pressure of 25 τ as rationalized above.…”

Section: On-line Sampling For Spectroscopy and Esi Msmentioning

confidence: 99%

Mechanistic and Kinetic Study of Singlet O₂ Oxidation of Methionine by On-Line Electrospray Ionization Mass Spectrometry

Liu

Yin

2015

J. Am. Soc. Mass Spectrom.

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Abstract. We report a reaction apparatus developed to monitor singlet oxygen ( 1 O 2 ) reactions in solution using on-line ESI mass spectrometry and spectroscopy measurements. 1O 2 was generated in the gas phase by the reaction of H 2 O 2 with Cl 2 , detected by its emission at 1270 nm, and bubbled into aqueous solution continuously. O 2 oxidation were monitored by UV-Vis absorption and positive/negative ESI mass spectra, and product structures were elucidated using collision-induced dissociation-tandem mass spectrometry. To suppress electrical discharge in negative ESI of aqueous solution, methanol was added to electrospray via in-spray solution mixing using theta-glass ESI emitters. Capitalizing on this apparatus, the reaction of 1 O 2 with methionine was investigated. We have identified methionine oxidation intermediates and products at different pH, and measured reaction rate constants.1 O 2 oxidation of methionine is mediated by persulfoxide in both acidic and basic solutions. Persulfoxide continues to react with another methionine, yielding methionine sulfoxide as end-product albeit with a much lower reaction rate in basic solution. Density functional theory was used to explore reaction potential energy surfaces and establish kinetic models, with solvation effects simulated using the polarized continuum model. Combined with our previous study of gas-phase methionine ions with 1 O 2 , evolution of methionine oxidation pathways at different ionization states and in different media is described.

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Section: On-line Sampling For Spectroscopy and Esi Msmentioning

confidence: 99%

Mechanistic and Kinetic Study of Singlet O₂ Oxidation of Methionine by On-Line Electrospray Ionization Mass Spectrometry

Liu

Yin

2015

J. Am. Soc. Mass Spectrom.

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“…The development of a robust asymmetric version is still an avidly sought goal. The MBH reaction, involving the attack of the intermediate enolate on aldehydes, has been widely studied both experimentally and computationally 4–7. By contrast, the RC reaction, where the enolate undergoes a Michael addition, has remained underdeveloped for many years due to the low selectivity and enantioselectivity of the process.…”

Section: Introductionmentioning

confidence: 99%

Rhodium(III)‐Catalyzed N‐Nitroso‐Directed CH Addition to Ethyl 2‐Oxoacetate for Cycloaddition/Fragmentation Synthesis of Indazoles

Chen

Song

et al. 2014

Chemistry A European J

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Rh(III) -catalyzed N-nitroso-directed CH addition to ethyl 2-oxoacetate allows subsequent construction of indazoles, a privileged heterocycle scaffold in synthetic chemistry, through the exploitation of reactivity between the directing group and installed group. The formal [2+2] cycloaddition/fragmentation reaction pathway identified herein, a unique reactivity pattern hitherto elusive for the N-nitroso group, emphasizes the importance of forward reactivity analysis in the development of useful CH functionalization-based synthetic tools. The synthetic utility of the protocol is demonstrated with the synthesis of a tricyclic-fused ring system. The diversity of covalent linkages available for the nitroso group should enable the extension of the genre of reactivity reported herein to the synthesis of other types of heterocycles.

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“…The MBH reaction, involving the attack of the intermediate enolate on aldehydes, has been widely studied both experimentally and computationally. [4][5][6][7] By contrast, the RC reaction, where the enolate undergoes a Michael addition, has remained underdeveloped for many years due to the low selectivity and enantioselectivity of the process. In 2007, one of our groups reported an enantioselective amino acid-catalyzed RC reaction that afforded the intermolecular RC reactions of bis-enones (see Scheme 1).…”

Section: Introductionmentioning

confidence: 99%

The Roles of Counterion and Water in a Stereoselective Cysteine‐Catalyzed Rauhut–Currier Reaction: A Challenge for Computational Chemistry

Osuna¹,

Dermenci²,

Miller³

et al. 2013

Chemistry A European J

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The stereoselective Rauhut-Currier (RC) reaction catalyzed by a cysteine derivative has been explored computationally with DFT (M06-2X) theory. Both methanethiol and a chiral cysteine derivative were studied as nucleophiles. The complete reaction pathway involves rate-determining elimination of the thiol catalyst from the Michael addition product. The stereoselective Rauhut-Currier reaction, catalyzed by a cysteine derivative as nucleophile, has also been studied in detail. This reaction was experimentally found to be extremely sensitive to the reaction conditions, such as the number of water equivalents and the effect of potassium counterion. The E1cB process for catalyst elimination has been explored computationally for the 8 possible stereoisomers. The effect of explicit water solvation and the presence of counterion (either K+ or Na+) has been studied for the lowest energy enantiomer pair (1S, 2R, 3S)/(1R, 2S, 3R).

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Brønsted Acid Catalyzed Morita–Baylis–Hillman Reaction: A New Mechanistic View for Thioureas Revealed by ESI‐MS(/MS) Monitoring and DFT Calculations

Cited by 74 publications

References 197 publications

Mechanistic and Kinetic Study of Singlet O₂ Oxidation of Methionine by On-Line Electrospray Ionization Mass Spectrometry

Mechanistic and Kinetic Study of Singlet O₂ Oxidation of Methionine by On-Line Electrospray Ionization Mass Spectrometry

Rhodium(III)‐Catalyzed N‐Nitroso‐Directed CH Addition to Ethyl 2‐Oxoacetate for Cycloaddition/Fragmentation Synthesis of Indazoles

The Roles of Counterion and Water in a Stereoselective Cysteine‐Catalyzed Rauhut–Currier Reaction: A Challenge for Computational Chemistry

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Brønsted Acid Catalyzed Morita–Baylis–Hillman Reaction: A New Mechanistic View for Thioureas Revealed by ESI‐MS(/MS) Monitoring and DFT Calculations

Cited by 74 publications

References 197 publications

Mechanistic and Kinetic Study of Singlet O2 Oxidation of Methionine by On-Line Electrospray Ionization Mass Spectrometry

Mechanistic and Kinetic Study of Singlet O2 Oxidation of Methionine by On-Line Electrospray Ionization Mass Spectrometry

Rhodium(III)‐Catalyzed N‐Nitroso‐Directed CH Addition to Ethyl 2‐Oxoacetate for Cycloaddition/Fragmentation Synthesis of Indazoles

The Roles of Counterion and Water in a Stereoselective Cysteine‐Catalyzed Rauhut–Currier Reaction: A Challenge for Computational Chemistry

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Mechanistic and Kinetic Study of Singlet O₂ Oxidation of Methionine by On-Line Electrospray Ionization Mass Spectrometry

Mechanistic and Kinetic Study of Singlet O₂ Oxidation of Methionine by On-Line Electrospray Ionization Mass Spectrometry