17072-58-1Relevant academic research and scientific papers
Catalyzed Radical Termination in the Presence of Tellanyl Radicals
Ribelli, Thomas G.,Rahaman, S. M. Wahidur,Matyjaszewski, Krzysztof,Poli, Rinaldo
supporting information, p. 13879 - 13882 (2017/10/13)
The decomposition of the diazo initiator dimethyl 2,2′-azobis(isobutyrate) (V-601), generating the Me2C.(CO2Me) radical, affords essentially the same fraction of disproportionation and combination in media with a large range of viscosity (C6D6, [D6]DMSO, and PEG 200) in the 25–100 °C range. This is in stark contrast to recent results by Yamago et al. on the same radical generated from Me2C(TeMe)(CO2Me) and on other X-TeR systems (X=polymer chain or unimer model; R=Me, Ph). The discrepancy is rationalized on the basis of an unprecedented RTe.-catalyzed radical disproportionation, with support from DFT calculations and photochemicaL V-601 decomposition in the presence of Te2Ph2.
Photoaddition reactions of 1,2-diketones with silyl ketene acetals. Formation of β-hydroxy-γ-ketoesters
Dae, Won Cho,Lee, Hyang-Yeol,Sun, Wha Oh,Jung, Hei Choi,Hea, Jung Park,Mariano, Patrick S.,Ung, Chan Yoon
, p. 4539 - 4547 (2008/09/20)
(Chemical Equation Presented) Photochemical reactions taking place between 1,2-diketones and silyl ketene acetals and their excited state reaction mechanisms have been explored. Irradiation of benzene, acetone, or acetonitrile solutions containing 1,2-diketones and silyl ketene acetals is observed to promote formation of 1,4-dioxenes, resulting from [4 + 2]-cycloaddition, oxetanes, arising by Paterno-Buchi processes, and β-hydroxy-γ- ketoesters, generated by SET-promoted Claisen-type condensation. These competitive pathways leading from the excited states of the 1,2-diketones to these products are influenced by solvent polarity and the nature of the silyl ketene acetal and 1,2-diketone. The Claisen-type condensation process, following an SET desilylation pathway and predominating when the photoreactions are carried out in the polar solvent acetonitrile, represents an efficient method to prepare a variety of diversely substituted β-hydoxy-γ-ketoesters.
Dissociation and Aromatization of a Semibenzene. Reactions of Triphenylmethyl and Methyl Isobutyryl Radicals
Engel, Paul S.,Chen, Yanqiu,Wang, Chengrong
, p. 3073 - 3079 (2007/10/02)
Semibenzene 4, which can be regarded as the recombination product of triphenylmethyl and methyl isobutyryl radicals (5), affords exactly these intermediates on thermolysis or inefficiently on direct photolysis.Recombination and disproportionation of these dissimilar radicals proceeds with a much lower barrier than the dimerization of triphenylmethyl.Whereas thiophenol or triplet 9-fluorenone aromatize 4, thermolysis in the presence of 1,4-cyclohexadiene allows trapping of 5 and oligomeric radical 13.From the measured heat of aromatization (22.0 kcal/mol), the C-H bond dissociation enthalpy of 4 and its analogue lacking the side chain ("p-isotriphenylmethane") is calculated to be 54 kcal/mol, the lowest value known for any closed-shell, neutral hydrocarbon.Exposure of 4 to the atmosphere causes rapid autoxidation to hydroperoxide 19, which thermolyzes in the GC to aromatic ketones and phenols instead of undergoing a 1,2-aryl shift.
DEHYDRODIMERIZATION OF KETONES, CARBOXYLIC ACIDS, AMIDES, ESTERS, ALCOHOLS, AND AMINES, VIA MERCURY-PHOTOSENSITIZATION
Boojamra, Constantine G.,Crabtree, Robert H.,Ferguson, Richard R.,Muedas, Cesar A.
, p. 5583 - 5586 (2007/10/02)
Selective dehydrodimerization of the title compounds can be carried out on a preparative scale at 1 atm. and at 25-110 deg C in a simple apparatus by Hg-photosensitized reaction under H2.
Photochemical Reactions of Arenecarboxylic Acid Esters with Electron-Rich Alkenes: 2 + 2 Cycloaddition, Hydrogen Abstraction, and Cycloreversion
Cantrell, Thomas S.,Allen, Andrew C.
, p. 135 - 139 (2007/10/02)
The photochemical reaction of arenecarboxylic acid methyl esters and isopropyl esters with alkenes has been examined and found to afford three types of products: (a) 2-alkoxyoxetanes 3 via a direct 2 + 2 cycloaddition to the substrate alkenes; (b) β,γ-unsaturated ketones 5 via hydrogen abstraction by the carbonyl oxygen of the photoexcited ester from an allylic position of the substrate alkene; and (c) alkoxyalkenes 4, which arise via 2 + 2 cycloreversion of the oxetanes 3.The quantum yields for the formation of the various products generally fell in the range 0.005-0.03, approximately 1 order of magnitude less than those of aryl ketones and aldehydes undergoing similar reactions.
The Cross-Reaction Between 1-Methoxycarbonyl-and 1-Butoxycarbonyl-1-methylethyl: Simultaneous Generation of Unlike Radicals from an Unsymmetrical Azo Precursor
Kelly, David P.,Serelis, Algirdas K.,Solomon, David H.,Thompson, Philip E.
, p. 1631 - 1639 (2007/10/02)
The title radicals (1a) and (1b) were generated simultaneously by thermolysis of the unsymmetrical diazene, butyl methyl azoisobutyrate (2d).In the presence of the radical scavenger 2,2,6,6-tetramethylpiperidin-1-yloxyl (4) the products of the geminate cross-reaction show that 45percent of radical pairs react by combination and 55percent by disproportionation.The disproportionation reaction shows a slight preference for hydrogen transfer from the butyl ester (1b) to the methyl ester (1a) radical.In the absence of scavenger (4), the encounter reactions of the two radicals show aslight preference for the cross-reaction over the two self-reactions which is most likely largely due to the imbalance in radical concentrations caused by the greater reactivity toward addition to olefins of the methyl ester radical.
The Self-Reactions of 1-Methoxycarbonyl-1-methylethyl and Higher Ester Radicals: Combination vs Disproportionation and Oligomeric Products from Secondary Reactions
Bizilj, Snezna,Kelly, David P.,Serelis, Algirdas K.,Solomon, David H.,White, Kathleen E.
, p. 1657 - 1673 (2007/10/02)
The geminate self-reactions of the title methyl, ethyl and butyl ester radicals (2a-c), formed by decomposition of the corresponding azo precursors (1a-c) in the presence of stable nitroxide radical scavengers, were found on the basis of product analysis to comprise combination and disproportionation in the ratios 56 : 44 (methyl), 58 : 42 (ethyl) and 47 : 53 (butyl).In the absence of radical scavengers, extensive oligomerization is observed.Hydrogenation and degradation were used in conjunction with g.l.c.-m.s. to deduce the identities of the dimeric, trimeric and tetrameric products, which were in most cases subsequently confirmed by isolation and n.m.r. analysis.Of particular interest is the highly regioselective disproportionation of radical (3) to give dimethyl 4-methylpent-1-ene-2,4-dicarboxylate (8), and the further reaction of (8) with (2a) to form branched oligomers (10) and (15).
