1016-09-7Relevant articles and documents
Finkelstein,Petersen
, p. 136,137 (1960)
Heldt
, p. 73,76 (1962)
Nafion-H Catalyzed Reductive Cleavage of Acetals and Ketals to Ethers with Triethylsilane
Olah, George A.,Yamato, Takehiko,Iyer, Pradeep,Prakash, G.K. Surya
, p. 2826 - 2828 (1986)
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Heat of reaction and reaction volume for the formation of ethers from diazo compounds in methanol
Yamaguchi, Shinji,Hirota, Noboru,Terazima, Masahide
, p. 284 - 290 (1998)
The heat of reaction and reaction volume for formation of ethers from several diazo compounds with two phenyl groups in methanol were determined by the transient grating and photoacoustic methods. It was found that the reaction volume significantly contri
Redox reaction of benzyl radicals with aromatic radical ions photogenerated. The Marcus inverted region and the selective formation of carbocations or carbanions
Ishiguro, Katsuya,Nakano, Tomoharu,Shibata, Hiroki,Sawaki, Yasuhiko
, p. 7255 - 7264 (1996)
Efficient redox reactions of benzyl-type radicals were achieved by irradiating an aromatic donor/acceptor pair with substituted dibenzyl ketones as a radical precursor in MeOH-MeCN. In this system, the aromatic radical ion pair was generated by photoinduced electron transfer followed by one-electron oxidation and reduction of photogenerated benzyl radicals (R·) by the radical ions to afford benzyl cations (R+) and anions (R-). The cations and anions were trapped by MeOH to yield ROMe and RH, respectively. The relative product ratios were determined for a variety of donor-acceptor pairs, reflecting the relative efficiencies of the redox reaction of benzyl radicals with a steady-state concentration of radical ions. The selective formation of carbocations or carbanions was achieved in some sets of donor/acceptor pairs. Assuming that the radical ions exist in a 1:1 ratio in the steady state, the product ratios are equal to the relative electron transfer rates, which are analyzed in terms of the free energy changes of the processes. The present results indicated that the rates became maximal at the energy gap of ca. -0.5 eV, representing a novel example of the Marcus inverted region. This interpretation is discussed in comparison with other related cases and in relation to recent theories on electron transfer rates.
New reaction of organic monohalides with orthoformates
Gazizov,Ibragimov,Khamidullina,Karimova,Pudovik,Sinyashin
, p. 1325 - 1326 (2005)
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Zon,G.,Paquette,L.A.
, p. 5478 - 5487 (1974)
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REACTION OF DIPHENYLCARBENE WITH METHANOL.
Griller,Nazran,Scaiano
, p. 198 - 202 (1984)
The reaction of triplet diphenylcarbene with methanol is believed to proceed via thermal excitation to the singlet state followed by reaction of that state with the alcohol. Analysis of the related reaction kinetics led to a reported enthalpy difference of 3-5 kcal mol** minus **1 between the singlet and its triplet ground state. The authors report measurements of the activation energy, E//o//b//s//d, for reaction of triplet diphenylcarbene with methanol in various solvents and find, for example, E//o//b//s//d equals 1. 66 plus or minus 0. 20 kcal mol** minus **1 in acetonitrile. These and other results are inconsistent with published interpretations of the data and dictate a reevaluation of earlier experiments and the mechanistic conclusions drawn from them.
Two-photon chemistry in the laser jet: Photoionization of the diphenylmethyl radical generated by norrish type I photocleavage of benzhydryl phenyl ketone
Adam, Waldemar,Oestrich, Rolf Schulte
, p. 6031 - 6034 (1992)
It is shown that in the laser jet (LJ) mode (argon ion laser) the benzhydryl phenyl ketone (1) undergoes a two-photon reaction in CC14 to yield benzhydryl chloride. The one-photon products are 1,1,2,2-tetraphenylethane (3), benzophenone, and 1,1,1-trichloro-2,2-diphenylethane (4). In methanol, on the other hand, our results suggest even a three-photon reaction in which benzhydryl methyl ether (5) is produced besides the one-photon products 3 and benzophenone. The ratios of the three-photon to one-photon products, i.e. 5 to 3, depended on the wavelength (333 or 351 nm). The three-photon mechanism was established by a competition experiment, in which ketone 1 was irradiated in mixtures of CCI4 and methanol. The ratio of the two high-intensity products ether 5 and benzhydryl chloride showed a strong intensity dependence. We propose that the electronically excited diphenylmethyl radical 2*is photochemically ionized to the diphenylmethyl cation 2+ under the high-intensity LJ photolysis conditions and the latter trapped with methanol and deuteriomethanol to give the identical benzhydryl methyl ether (5). The fact that no deuterium-incorporated ether 5 was observed eliminates the carbene mechanism proposed in the literature, at least under our LJ photolysis conditions.
Biphotonic generation of carbenes and carbocations by laser flash photolysis
Kirmse, Wolfgang,Krzossa, Birgit,Steenken, Steen
, p. 1197 - 1200 (1996)
In protic solvents, trans-2,3-diphenylaziridinylimines of diaryl ketones are (flash-)photolyzed in two consecutive steps, via diaryldiazomethanes and diarylcarbenes, to give eventually diarylmethyl cations. The same intermediates arise from diazo ketones by way of Wolff rearrangement and ketene photolysis. The method has been used to demonstrate the protonation of fluorenylidene by hexafluoroisopropanol.
Reaction of Diphenylcarbene with Diphenyldiazomethane
Griller, D.,Majewski, M.,McGimpsey, W. G.,Nazran, A. S.,Scaiano, J. C.
, p. 1550 - 1553 (1988)
The reaction of diphenylcarbene with diphenyldiazomethane, which leads to the corresponding azine, has been examined by a combination of laser flash photolysis techniques and product studies.In acetonitrile at room temperature, the apparent rate constants
Stedronsky et al.
, p. 993 (1968)
Arrhenius Parameters for Hydrogen and Chlorine Atom Abstraction Reactions of Triplet Diphenylcarbene and Dibenzocycloheptadiene
Barcus, Robert L.,Platz, Matthew S.,Scaiano, J. C.
, p. 695 - 699 (1987)
The absolute kinetics of the reaction of triplet diphenylcarbene (DPC) and dibenzocycloheptadienylidene (DBC) were measured with various atom donors as a function of temperature.Diethyl ether and toluene were used as hydrogen atom donors and carbon tetrac
Photolysis of Triphenylacetic Acid and Its Methyl Ester: A Novel Photochemical Generation of Carbene Intermediates
Shi, Min,Okamoto, Yoshiki,Takamuku, Setsuo
, p. 3345 - 3347 (1990)
The photolysis of methyl triphenylacetate in methanol gave biphenyl, methyl α-methoxyphenylacetate, methyl benzoate, and methoxydiphenylmethane.The formation of these products suggests that two types of α,α-elimination take place: One is the elimination of two phenyl groups leaving Ph-C-CO2Me (type a), and the other is the elimination of the phenyl and methoxycarbonyl groups generating Ph2C: (type b).Only type a elimination was efficiently quenched by oxygen.
TEMPERATURE DEPENDENCE OF THE REACTIONS OF SINGLET AND TRIPLET DIPHENYLCARBENE. EVIDENCE FOR REVERSIBLE YLIDE FORMATION IN THE REACTION WITH ALCOHOLS
Turro, Nicholas J.,Cha, Yuan,Gould, Ian R.
, p. 5951 - 5954 (1985)
The temperature dependences of the reaction of singlet diphenylcarbene are consistent with reversible intermediate formation.
Wladislaw et al.
, p. 586 (1966)
Decarboxylative cross-nucleophile coupling via ligand-to-metal charge transfer photoexcitation of Cu(ii) carboxylates
Li, Qi Yukki,Gockel, Samuel N.,Lutovsky, Grace A.,DeGlopper, Kimberly S.,Baldwin, Neil J.,Bundesmann, Mark W.,Tucker, Joseph W.,Bagley, Scott W.,Yoon, Tehshik P.
, p. 94 - 99 (2022/01/11)
Reactions that enable carbon–nitrogen, carbon–oxygen and carbon–carbon bond formation lie at the heart of synthetic chemistry. However, substrate prefunctionalization is often needed to effect such transformations without forcing reaction conditions. The development of direct coupling methods for abundant feedstock chemicals is therefore highly desirable for the rapid construction of complex molecular scaffolds. Here we report a copper-mediated, net-oxidative decarboxylative coupling of carboxylic acids with diverse nucleophiles under visible-light irradiation. Preliminary mechanistic studies suggest that the relevant chromophore in this reaction is a Cu(ii) carboxylate species assembled in situ. We propose that visible-light excitation to a ligand-to-metal charge transfer (LMCT) state results in a radical decarboxylation process that initiates the oxidative cross-coupling. The reaction is applicable to a wide variety of coupling partners, including complex drug molecules, suggesting that this strategy for cross-nucleophile coupling would facilitate rapid compound library synthesis for the discovery of new pharmaceutical agents. [Figure not available: see fulltext.].
Benzyl C–O and C–N Bond Construction via C–C Bond Dissociation of Oxime Ester under Visible Light Irradiation
Fan, Xiuwei,Lei, Tao,Liu, Zan,Yang, Xiu-Long,Cheng, Yuan-Yuan,Liang, Ge,Chen, Bin,Tung, Chen-Ho,Wu, Li-Zhu
, p. 1551 - 1558 (2019/09/09)
A photoredox benzyl activation was developed via formidable C(sp3)–C(sp3) bond dissociation of 1-aryl acetone oxime esters, which were easily prepared from benzyl ketones. Further coupling with O- and N- nucleophiles successfully forged important benzyl ether and amines derivatives in one pot. In this process, different substitutions on oxime esters were found compatible and various primary and secondary alcohols and amines, as well as amides showed good performance as nucleophiles. Mechanistic studies by control experiments, electrochemical measurements and in-situ NMR spectra proposed a N–O bond interruption/C–C bond fragmentation/oxidation sequence to provide the key cation intermediate for the next electrophilic SN process. The features of mild condition, short reaction time and broad substrate scope made this new strategy much promising in the transformation of benzyl compounds, which might be valuable in last-stage functionalizations.
Understanding the Chemoselectivity in Palladium-Catalyzed Three-Component Reaction of o-Bromobenzaldehyde, N-Tosylhydrazone, and Methanol
Huang, Xueliang,Ren, Xiaojian,Wang, Zhi-Xiang,Yu, Yinghua,Zhu, Lei
supporting information, (2020/04/10)
To understand the ligand-controlled palladium-catalyzed coupling of o-bromobenzaldehyde, N-tosylhydrazone, and methanol to give methyl 2-benzylbenzoic ester or methyl ether, we herein investigated the mechanisms which account for how C-C and C-O bonds are
