Products from photochemical reactions and electrochemical oxidation of methylenecyclopropane

1997 ◽  
Vol 75 (12) ◽  
pp. 1795-1809 ◽  
Author(s):  
H.J.P. de Lijser ◽  
T. Stanley Cameron ◽  
Donald R. Arnold
Keyword(s):  
Electron Transfer ◽  
Ionization Potential ◽  
Radical Cation ◽  
Photoinduced Electron Transfer ◽  
Nucleophilic Addition ◽  
Major Product ◽  
Oxidation Potential ◽  
Photochemical Reactions ◽  
Tert Butyl ◽  
Adiabatic Ionization Potential

The reactivity of methylenecyclopropane (MCP, 1) and its radical cation (1+•) have been studied in the presence and absence of a nucleophile (methanol). Photochemical reactions of 1 in the presence of an electron-acceptor (1,4-dicyanobenzene, 6) and a codonor (biphenyl, 7) in acetonitrile (with and without methanol present) or chloroform lead to cycloadditions (ortho, meta, and para; products 12–17) rather than products from photoinduced electron transfer (PET). Based on the measured (cyclic voltammetry, CV) oxidation potential, using the Weller equation, electron transfer (ET) was predicted to occur. It was shown that the measured oxidation potential of 1 represents the adiabatic ionization potential. For PET processes the value for the vertical ionization potential must be used. Electrochemical (EC) generation of 1+• without a nucleophile present results in the formation of one major product: tert-butyl acetamide (25). A series of rearrangements leading to the tert-butyl cation is proposed. Addition of a nucleophile (methanol) to the mixture leads to the formation of 3-methoxy-2-(methoxymethyl)-1-propene (26). This product may arise from trapping of the initially formed ring-opened (trimethylenemethane) radical cation (1a+•), which undergoes a second oxidation and nucleophilic addition (ECE). Keywords: methylenecyclopropane, radical cation, photochemistry, electrochemistry, photocycloaddition.

A stable, highly oxidizing radical cation

2020 ◽  
Vol 44 (42) ◽  
pp. 18138-18148
Author(s):  
N. Harsha Attanayake ◽  
Aman Preet Kaur ◽  
T. Malsha Suduwella ◽  
Corrine F. Elliott ◽  
Sean R. Parkin ◽  
...  
Keyword(s):  
Ionization Potential ◽  
Radical Cation ◽  
Oxidation Potential ◽  
Adiabatic Ionization Potential ◽  
Half Wave

Changes in adiabatic ionization potential and half wave oxidation potential with ortho and para substitution on an N-alkylated phenothiazine.

Radical ions in photochemistry. 21. The photosensitized (electron transfer) tautomerization of alkenes; the phenyl alkene system

1989 ◽  
Vol 67 (4) ◽  
pp. 689-698 ◽  
Author(s):  
Donald R. Arnold ◽  
Shelley A. Mines
Keyword(s):  
Hydrogen Bond ◽  
Electron Transfer ◽  
Radical Cation ◽  
Radical Anion ◽  
Phenyl Group ◽  
Oxidation Potential ◽  
Original Position ◽  
Acetonitrile Solution ◽  
Steric Interaction ◽  
Ambident Anion

Alkenes, conjugated with a phenyl group, can be converted to nonconjugated tautomers by sensitized (electron transfer) irradiation. For example, irradiation of an acetonitrile solution of the conjugated alkene 1-phenylpropene, the electron accepting photosensitizer 1,4-dicyanobenzene, the cosensitizer biphenyl, and the base 2,4,6-trimethylpyridine gave the nonconjugated tautomer 3-phenylpropene in good yield. Similarly, 2-methyl-1-phenylpropene gave 2-methyl-3-phenylpropene, and 1-phenyl-1-butene gaveE- and Z-1-phenyl-2-butene. The reaction also works well with cyclic alkenes. For example, 1-phenylcyclohexene gave 3-phenylcyclohexene, and 1-(phenylmethylene)cyclohexane gave 1-(phenylmethyl)cyclohexene. The proposed mechanism involves the initial formation of the alkene radical cation and the sensitizer radical anion, induced by irradiation of the sensitizer and mediated by the cosensitizer. Deprotonation of the radical cation assisted by the base gives the ambident radical, which is then reduced to the anion by the sensitizer radical anion. Protonation of the ambident anion at the benzylic position completes the sequence. Reprotonation at the original position is an energy wasting step. Tautomerization is driven toward the isomer with the higher oxidation potential, which is, in the cases studied, the less thermodynamically stable isomer. The regioselectivity of the deprotonation step is dependent upon the conformation of the allylic carbon–hydrogen bond. The tautomerization of 2-methyl- 1-phenylbutene gave both 2-phenylmethyl-1-butène and 2-methyl-1-phenyl-2-butene (E and Z isomers), while 2,3-dimethyl- 1-phenylbutene gave only 3-methyl-2-phenylmethyl-1 -butene. In the latter case, steric interaction of the methyls on the isopropyl group prevents effective overlap of the tertiary carbon–hydrogen bond with the singly occupied molecular orbital, thus inhibiting deprotonation from this site. Keywords: photosensitized, electron transfer, alkene, tautomerization, radical cation.

Photoinduced electron-transfer reactions: rearrangement of a bicyclopropenyl radical cation

1985 ◽  
Vol 107 (13) ◽  
pp. 3840-3843 ◽  
Author(s):  
Christopher J. Abelt ◽  
Heinz D. Roth
Keyword(s):  
Electron Transfer ◽  
Radical Cation ◽  
Photoinduced Electron Transfer ◽  
Transfer Reactions ◽  
Electron Transfer Reactions

Photochemical nucleophile–olefin combination, aromatic substitution (photo-NOCAS) reaction. Part 6: methanol, nonconjugated dienes, and 1,4-dicyanobenzene

1994 ◽  
Vol 72 (2) ◽  
pp. 415-429 ◽  
Author(s):  
Donald R. Arnold ◽  
Kimberly A. McManus ◽  
Xinyao Du
Keyword(s):  
Electron Transfer ◽  
Double Bond ◽  
Radical Cation ◽  
Oxidation Potential ◽  
Aromatic Substitution ◽  
Double Bonds ◽  
Excited Singlet ◽  
Reaction Conditions ◽  
Methanol Solutions ◽  
Cyclic Adducts

Irradiation, through Pyrex, of an acetonitrile–methanol (3:1) solution of 1,4-dicyanobenzene (1) and 1,5-hexadiene (9) leads to formation of ortho and meta cyclic adducts (13–16) arising from the intermediate exciplex. There was no evidence for interaction between the two double bonds of this nonconjugated diene. The oxidation potential of 9 is high enough (> 3 V vs. sce) to preclude single electron transfer (SET); no photo-NOCAS products are formed. Similar irradiation of acetonitrile–methanol solutions of 1 and 2-methyl-1,5-hexadiene (10) does yield a photo-NOCAS product (17); reaction occurs only on the more heavily substituted double bond. The additional substitution on the double bond lowers the oxidation potential (2.70 V vs. sce) of this diene to the point where SET from 10 to the excited singlet state of 1 can occur. In this case, no cycloaddition products are formed; the exciplex is quenched by electron transfer. There was no evidence for interaction between the two double bonds of the initially formed radical cation 10+•, or between the terminal double bond and the β-alkoxyalkyl radical of the intermediate leading to the photo-NOCAS product. The photo-NOCAS product (19) was also formed when 2,5-dimethyl-1,5-hexadiene (11) was subjected to these reaction conditions. In this case, when biphenyl (4) was added as a codonor, in addition to the photo-NOCAS product, products (21cis and trans) resulting from cyclization of the initially formed acyclic radical cation 11+• to give the 1,4-dimethylcyclohexane-1,4-diyl radical cation were also observed. This 1,6-endo, endo cyclization of 11+• must be rapid enough to compete with reaction with methanol. There was no evidence for cyclization (neither 1,4-exo nor 1,5-endo) of the intermediate β-alkoxyalkyl radical. When the radical cation of 2,5-dimethyl-1,4-hexadiene (12+•) is generated under these reaction conditions, photo-NOCAS products 22 and 23 are formed at the more heavily substituted double bond, along with the conjugated tautomer 2,5-dimethyl-2,4-hexadiene (24). The mechanisms for these transformations are discussed.

scholarly journals Photoinduced electron transfer in 2- tert -butyl-3-(anthracen-9-yl)-2,3-diazabicyclo[2.2.2]octane

2006 ◽  
Author(s):  
Guadalupe Valverde-Aguilar ◽  
Jorge Garcia-Macedo ◽  
Xianghuai Wang ◽  
Jeffrey I. Zink ◽  
Stephen F. Nelsen
Keyword(s):  
Electron Transfer ◽  
Photoinduced Electron Transfer ◽  
Tert Butyl

Article

1999 ◽  
Vol 77 (10) ◽  
pp. 1655-1670 ◽  
Author(s):  
Dino Mangion ◽  
Donald R Arnold
Keyword(s):  
Electron Transfer ◽  
Photoinduced Electron Transfer ◽  
Photochemical Reactions ◽  
Transfer Mechanism ◽  
Radical Ions ◽  
Reaction Conditions ◽  
Electron Transfer Mechanism ◽  
Photochemical Reactivity ◽  
Bond Homolysis

The photochemical reactivity of a series of 4-halobenzonitriles and 4-haloanisoles with 1,1-diphenylethene in a nucleophilic solvent (methanol) has been investigated. Analysis of the photochemical reactions involving the 4-halobenzonitriles revealed formation of alkene-methanol adducts, such as 1-methoxy-2,2-diphenylethane, 1-methoxy-2,2-diphenylethene, and 1,1-dimethoxy-2,2-diphenylethane, indicative of a photochemical electron-transfer mechanism. These products were not significant in the photochemical reactions involving the 4-haloanisoles. Both the 4-halobenzonitriles and the 4-haloanisoles produced an arene-alkene-methanol Markovnikov adduct, 1-aryl-2-methoxy-2,2-diphenylethane (aryl = 4-cyanophenyl or 4-methoxyphenyl). This compound was shown to undergo an acid-catalysed elimination to 1-aryl-2,2-diphenylethene under the reaction conditions, which subsequently underwent a 6pi-electrocyclization to the 3-substituted(cyano or methoxy)-9-phenylphenanthrene. Possible mechanisms for the observed reactivity are discussed and evaluated.Key words: photochemistry, photoinduced electron transfer, bond homolysis, radical ions, radicals, exciplexes.

Photoinduced Electron Transfer-Initiated Enantioselective Cyclization of N-Benzoyl-α-dehydroarylalanine tert-Butyl Esters in the Presence of Chiral Amine

Heterocycles ◽  
2007 ◽  
Vol 74 (1) ◽  
pp. 149 ◽  
Author(s):  
Tadamitsu Sakurai ◽  
Haruo Watanabe ◽  
Kei Maekawa ◽  
Tetsutaro Igarashi
Keyword(s):  
Electron Transfer ◽  
Photoinduced Electron Transfer ◽  
Chiral Amine ◽  
Tert Butyl ◽  
Butyl Esters

Rearrangement of a 2-Methylenecyclobutanone Derivative Triggered by Photoinduced Electron Transfer:  An Unprecedented Oxa Analogue of the Tetramethyleneethane Radical Cation

2004 ◽  
Vol 126 (2) ◽  
pp. 414-415 ◽  
Author(s):  
Hiroshi Ikeda ◽  
Futoshi Tanaka ◽  
Kimio Akiyama ◽  
Shozo Tero-Kubota ◽  
Tsutomu Miyashi
Keyword(s):  
Electron Transfer ◽  
Radical Cation ◽  
Photoinduced Electron Transfer
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