Triplet-state energies and substituent effects of excited aroyl compounds in the gas phase

Lin, Zhongping John; Aue, Walter A.

doi:10.1016/s1386-1425(99)00122-5

Cited by 27 publications

(18 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The α,β‐unsaturated aldehydes 6 , which serve as precursors for 4 , exhibit a higher triplet energy than the respective salts. The triplet energy of cinnamic aldehyde ( 6 a ) for example has been determined as E T =300 kJ mol −1 . As a consequence, a negligible sensitized conversion is to be expected if 6 a is irradiated in the presence of 2,3‐dimethylbutadiene under the reaction conditions shown in Scheme .…”

Section: Resultsmentioning

confidence: 99%

Triplet Energy Transfer from Ruthenium Complexes to Chiral Eniminium Ions: Enantioselective Synthesis of Cyclobutanecarbaldehydes by [2+2] Photocycloaddition

et al. 2020

View full text Add to dashboard Cite

Chiral eniminium salts, prepared from α,β‐unsaturated aldehydes and a chiral proline derived secondary amine, underwent, upon irradiation with visible light, a ruthenium‐catalyzed (2.5 mol %) intermolecular [2+2] photocycloaddition to olefins, which after hydrolysis led to chiral cyclobutanecarbaldehydes (17 examples, 49–74 % yield), with high diastereo‐ and enantioselectivities. Ru(bpz)3(PF6)2 was utilized as the ruthenium catalyst and laser flash photolysis studies show that the catalyst operates exclusively by triplet‐energy transfer (sensitization). A catalytic system was devised with a chiral secondary amine co‐catalyst. In the catalytic reactions, Ru(bpy)3(PF6)2 was employed, and laser flash photolysis experiments suggest it undergoes both electron and energy transfer. However, experimental evidence supports the hypothesis that energy transfer is the only productive quenching mechanism. Control experiments using Ir(ppy)3 showed no catalysis for the intermolecular [2+2] photocycloaddition of an eniminium ion.

show abstract

Section: Resultsmentioning

confidence: 99%

Triplet Energy Transfer from Ruthenium Complexes to Chiral Eniminium Ions: Enantioselective Synthesis of Cyclobutanecarbaldehydes by [2+2] Photocycloaddition

et al. 2020

View full text Add to dashboard Cite

show abstract

“…Anthracene is acting asatriplet-state quencher [energy of triplet state (ET) (anthracene) = 176 kJ mol À1 [21] vs. ET (4-cyanobenzaldehyde) = 288 kJ mol À1 [22] ]a nd effectively quenches 4-cyanobenzaldehyde. This constitutes evidencet hat the triplets tate of 4-cyanobenzaldehyde is involved in the mechanism.…”

Section: Resultsmentioning

confidence: 99%

Photochemical Hydroacylation of Michael Acceptors Utilizing an Aldehyde as Photoinitiator

2019

View full text Add to dashboard Cite

The hydroacylation of Michael acceptors constitutes a useful tool for the formation of new C−C bonds. In this work, an environmentally friendly procedure was developed, utilizing 4cyanobenzaldehyde as the photoinitiator and household bulbs as the irradiation source. A great variety of substrates was well‐tolerated, leading to good yields, and mechanistic experiments were performed to elucidate the catalyst's possible mechanistic pathway. Moreover, the inherent selectivity challenge regarding α,α‐disubstituted aldehydes (decarbonylation problem) was studied and addressed.

show abstract

“…Thus, the electron‐donating substituents which increase the electron density at the reaction center (carbon C5 in the oxazolone ring) distinctly slow down the ring‐opening reaction with the nucleophile. An influence of substituents on a reaction rate is usually correlated with the substituent constants using the Hammett equation 21–25 or its modifications 6, 26–28. In our studies we used the classical Hammett equation log ( k / k 0 ) = ρσ, where k and k 0 are rate constants obtained for substituted and unsubstituted Ox, respectively, ρ is a reaction constant, and σ is a substituent constant.…”

Section: Resultsmentioning

confidence: 99%

“…In organic chemistry many empirical models for a description of relations between structure and reactivity have emerged. The most successful model describing an influence of substituents on the reaction rate was based on the classical Hammett equation 21–25 and its further modifications 16, 26–29. The Hammett model assumed a direct correlation between the influence of substituents on the reaction rate and substituent constants σ, which were defined as independent in the studied reaction.…”

Section: Introductionmentioning

confidence: 99%

Reaction of 4‐benzylidene‐2‐methyl‐5‐oxazolone with amines, Part 2: Influence of substituents in para‐position in the phenyl ring and a substituent on amine nitrogen atom on the reaction kinetics

Betłakowska¹,

Banecki²,

Czaplewski³

et al. 2002

Int J of Chemical Kinetics

View full text Add to dashboard Cite

An influence of a structure of the amine (benzylamine, N-methyl-benzylamine, N-isopropyl-benzylamine, N-methyl-butylamine, N-ethyl-butylamine, sec-butylamine, and tertbutylamine) on a rate constant of the ring-opening reaction of 4-benzylidene-2-methyl-5-oxazolone (Ox) was studied. The good correlation between logarithm of the rate constants and Charton's steric substituent constant ν as well as good correlation with a form of the simple branching equation indicate that there is a steric effect because of substitution at C1 carbon atom of nucleophile which decreases the reaction rate. Additionally, an influence of a structure of the benzylidene moiety of Ox on a rate of the oxazolone ring-opening reaction was studied. REACTION OF 4-BENZYLIDENE-2-METHYL-5-OXAZOLONE WITH AMINES 149The substituents ( OH, OCH 3 , N(CH 3 ) 2 , Cl, NO 2 ) in para-position of the phenyl ring of Ox substantially modified the rate of the reaction with benzylamine in acetonitrile. The rate of the Ox ring-opening reaction decreased with increase of the electron-donating properties of the substituent. A good correlation between the rate constants of the reaction of 4-(4 -substitutedbenzylidene)-2-methyl-5-oxazolones with benzylamine and the electron density at the reaction center (carbon C5 of the oxazolone ring), calculated using ab initio method, and the Hammett substituent constants, and CR equation were established.

show abstract

Triplet-state energies and substituent effects of excited aroyl compounds in the gas phase

Cited by 27 publications

References 17 publications

Triplet Energy Transfer from Ruthenium Complexes to Chiral Eniminium Ions: Enantioselective Synthesis of Cyclobutanecarbaldehydes by [2+2] Photocycloaddition

Triplet Energy Transfer from Ruthenium Complexes to Chiral Eniminium Ions: Enantioselective Synthesis of Cyclobutanecarbaldehydes by [2+2] Photocycloaddition

Photochemical Hydroacylation of Michael Acceptors Utilizing an Aldehyde as Photoinitiator

Reaction of 4‐benzylidene‐2‐methyl‐5‐oxazolone with amines, Part 2: Influence of substituents in para‐position in the phenyl ring and a substituent on amine nitrogen atom on the reaction kinetics

Contact Info

Product

Resources

About