- A Self-Assembled Cage with Endohedral Acid Groups both Catalyzes Substitution Reactions and Controls Their Molecularity
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A self-assembled Fe4L6 cage complex internally decorated with acid functions is capable of accelerating the thioetherification of activated alcohols, ethers and amines by up to 1000-fold. No product inhibition is seen, and effective
- Bogie, Paul M.,Holloway, Lauren R.,Ngai, Courtney,Miller, Tabitha F.,Grewal, Divine K.,Hooley, Richard J.
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supporting information
p. 10232 - 10238
(2019/07/09)
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- Iodine-catalyzed disproportionation of aryl-substituted ethers under solvent-free reaction conditions
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Iodine was demonstrated to be an efficient catalyst for disproportionation of aryl-substituted ethers under solvent-free reaction conditions. Variously substituted 1,1,1′,1′-tetraaryldimethyl ethers were transformed into the corresponding diarylketone and diarylmethane derivatives. I 2-catalyzed transformation of 4-methoxyphenyl substituted ethers yielded mono- and dialkylated Friedel-Crafts products as well. Treatment of trityl alkyl and trityl benzyl ethers with a catalytic amount of iodine produced triphenylmethane and the corresponding aldehydes and ketones. The electron-donating substituents facilitated the reaction, while the electron-withdrawing groups retarded it; the difference in reactivity is not very high. Such an observation may be in favour of hydride transfer, predominantly from the less electron rich side of the ether with more stable carbocation formation. With the isotopic studies it was established that a substantial portion of the C-H bond scission took place in the rate-determining step, while the carbonyl oxygen atom originated from the starting ether, and not from the air. The transformation took place under air and under argon, and HI was not a functioning catalyst.
- Jereb, Marjan,Vrazic, Dejan
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p. 1978 - 1999
(2013/05/22)
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- Decarboxylative photooxygenation of arylacetic acids by using mercuric oxide
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A new method for decarboxylative photooxygenation of arylacetic acids is developed by using light sensitive HgO in MeCN-MeOH which leads to aldehydes and ketones in high yield through trapping of benzylic radical intermediates by dioxygen.
- Habibi, Mohammad H.,Farhadi, Saeid
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p. 296 - 297
(2007/10/03)
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- Tetrazoles: XLIV. Synthesis and chemical properties of 5-substituted 2-triphenylmethyltetrazoles
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Tritylation of tetrazole and its 5-substituted derivatives with triphenylmethyl chloride under conditions of phase-transfer catalysis regioselectively yields the corresponding 5-substituted 2-trityltetrazoles which can be used to protect N-H bonds in nitrogen-containing heterocycles and O-H bonds in primary alcohols. Thermolysis of 2-trityltetrazoles in benzonitrile leads to 3,6-disubstituted 1,2,4,5-tetrazines. Thermal transformation of the same compounds in dodecane follows a radically different mechanism, resulting in formation of difficultly accessible 8,8-diphenylheptafulvenes. The structure of the latter was proved by X-ray analysis.
- Myznikov,Artamonova,Bel'skii,Stash,Skvortsov,Koldobskii
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p. 1360 - 1369
(2007/10/03)
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- Reductive demercuration in deprotection of trityl thioethers, trityl amines, and trityl ethers
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A room-temperature deprotection method of trityl amines, -ethers, and -thioethers is presented, based on coupling of metal acid catalysis (HgX2, with X- = Cl- or OAc-) and sodium borohydride reduction. The results of its application to monotritylated compounds (ethanethiol, ethanol, and piperidine) and to mono- and ditritylated 1,2-bifunctional compounds (mercaptoethanol, aminoethanethiol, and ethanolamine) are compared with those obtained with early methods based on the use of strong Bronsted acids (pure TFA and MeCN solutions of HCl). Trityl thioethers of simple thiols and amino and hydroxy thiols are promptly cleaved by reductive detritylation, and one-pot procedures can be employed to produce free thiols. In contrast, dilution with water of these same compounds in solutions of strong Bronsted acids leaves them unaffected. O-Tr and N-Tr bonds are broken by this latter treatment. However, trityl ethers are rapidly cleaved by even dilute HCl solutions, while cleaving of trityl amines is modulated by HCl concentration. Addition of NaBH4 to solutions of monofunctional trityl ethers in HgCl2/MeCN leads to complete deprotection. Monofunctional trityl amines are partially deprotected only if the complexation reaction is allowed to reach equilibrium. Combination of H+- with HgX+-catalyzed detritylation methods allows selective deprotection of pertritylated amino and hydroxy thiols. The results appear to be due to the strong difference in the affinity of the donor atoms present in the pertritylated substrates for H+ and HgX+. Catalysis based on Bronsted acids leads to cleaving of the N- and O-trityl bonds with recovering of the S-trityl group; that based on mercury salts allows recovering of N- and O-trityl groups with deprotection of the -SH function. Selectivity in deprotection of pertritylated amino alcohols seems to be severely hampered by similarity in the affinity of N- and O-atoms for H+ and HgX+, and, taking advantage of the lower HgX+-complexation rate of the N-trityl with respect to the O-trityl group, only preservation of the N-trityl bond has been achieved.
- Maltese
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p. 7615 - 7625
(2007/10/03)
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- Cerium(IV), as a selective and efficient catalyst for alcoholyses of allylic and tertiary benzylic alcohols
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An efficient and selective method is described for the catalytic conversion of allylic, and tertiary benzylic alcohols into their corresponding ethers in the presence of Ce(IV) under solvolytic and non- solvolytic conditions.
- Iranpoor, Nasser,Mothaghineghad, Enayatholah
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p. 1859 - 1870
(2007/10/02)
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- Catalytic and Efficient Cleavage of Allylic and Tertiary Benzylic Ethers and Esters with Ce(IV)
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The reaction of cerium(IV) as ceric ammonium nitrate (CAN) with a variety of allylic and tertiary benzylic ethers and esters has been examined in different alcohols and acetic acid under catalytic and mild conditions.Experiments have been conducted to elu
- Iranpoor, Nasser,Mottaghinejad, Enayatolah
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p. 7299 - 7306
(2007/10/02)
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- The Reaction of Triphenylmethyl Halides with Tributylphosphine and Tributylamine in Apolar Solvents
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Triphenylmethyl bromide (1a) and chloride (1b) react with tributylphosphine and tributylamine in aromatic hydrocarbons by single electron transfer.The triphenylmethyl radicals produced (which may be detected by e.s.r. spectroscopy) abstract hydrogen from the solvent or the radical cations of the reagents to give triphenylmethane (1c), and are trapped by oxygen to give triphenylmethylperoxy radicals and subsequently benzophenone, triphenylmethanol (1d), and phenol.Tributylphosphine and tributylamine may act as hydrogen donors in the hydrogen-transfer processes involved in the formation of these oxygenation products.The halides (1a, b) and tributylphosphine furnish, in the absence of oxygen, in addition to triphenylmethane (1c) the tele substitution products (2a) and (2b), respectively.There is some evidence that the phosphonium salt (2a) is formed by an S'ET process, i.e. out-of-cage recombination of triphenylmethyl radicals and tributylphosphine radical cations or tributylphosphine.
- Huszthy, Peter,Izso, (nee Gergacz) Gyoengyi,Lempert, Karoly,Kajtar-Peredy, Maria,Gyoer, Miklos,et al.
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p. 1513 - 1520
(2007/10/02)
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- Synthesis of ent-Kaurene from a Naturally Occurring Precursor
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ent-Kaurene (1) has been synthesized from a naturally occurring precursor, ent-kaurane-17,19-diol (3a).Selective deoxygenation at C19 of the diol was achieved after the C17 hydroxyl was protected as the triphenylmethyl ether. ent-Kaurene was then prepared by way of an elimination sequence at C17.
- Hogg, Ronald W.,Knox, John R.
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p. 469 - 474
(2007/10/02)
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- Regioselective N- or O-Tritylation of 2(1H)-Pyridone - (Triphenylmethyl)pyridones as Tritylation Agents
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Tritylation of 2(1H)-pyridone (1) with triphenylmethyl chloride (4) in acetonitrile leads exclusively to N-trityl-2(1H)-pyridone (3a) via the lithium salt 1', whereas 2-pyridyl trityl ether (3b) is the only product from the reaction with the sodium salt 1
- Effenberger, Franz,Brodt, Werner,Zinczuk, Juan
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p. 3011 - 3026
(2007/10/02)
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- ISOSELECTIVITY RELATION IN THE SOLVOLYSIS OF SUBSTITUTED TRITYL AND m-CHLOROTRITYL BENZOATES IN AQUEOUS ETHANOL
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The rate constants for the solvolysis of two series of trityl benzoates XC6H4(C6H5)2COC(O)C6H4Y in aqueous ethanol (80-100percent) were determined by potentiometric titration, and the activation and correlation parameters were calculated.In series (I) the effect of the substituent Y on the reaction rate in 100percent ethanol is due to entropic control.The isoselectivity temperature (Tis) lies in the region of 25 deg C.An inverse relation between the reactivity and selectivity (ρ, m) is observed when T > Tis, and this is regarded as the consequence of the predominance of solvation effects, which appear at the stage of the transition from intimate to loose ion pairs, over electronic effects.In the more reactive series (II) the effect of solvation decreases, the activation parameters level out, and the Tis value becomes less than the determined value.
- Karavan, V. S.,Eliseeva, E. E.
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p. 657 - 662
(2007/10/02)
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- Studies on the Development of the Tritylsulfenyl Group as a Nitrogen Protecting Group and Application in a Synthesis of δ-Coniceine
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The (triphenylmethyl)sulfenyl (tritylsulfenyl, TRS) group was found to posses properties which should make it useful as a nitrogen protecting group.The almost instantaneous reaction of TrSCl (6) with amines produced the corresponding triphenylmethanesulfenamides.The TRS group was found to render the nitrogen atom nonbasic and relatively nonnucleophilic, was stable to aqueous acid, aqueous base, and various reducing agents, and was moderately stable to Moffat oxidation conditions.The TRS group could be cleaved under mild conditions, generating the amine with either CuCl2/EtOH-THF, HI/THF-H2O, or trimethylsilyl iodide (Me3SiI)/CH2Cl2.A synthesis of δ-coniceine (16) illustrates carbon-carbon bond formation with tritylsulfenimine methodology and the utility of the tritylsulfenyl group as a nitrogen protecting group.
- Branchaud, Bruce P.
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p. 3538 - 3544
(2007/10/02)
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- A FACILE PROCEDURE FOR O-TRITYLATION
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The title operation is achieved via readily accessible organosilicon compounds.
- Murata, S.,Noyori, R.
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p. 2107 - 2108
(2007/10/02)
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- TRIMETHYLSILYL TRIFLATE IN ORGANIC SYNTHESIS
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Trimethylsilyl triflate is a powerful silylating agent for organic compounds and acts as a catalyst which accelerates a variety of nucleophilic reactions in aprotic media.The reactions proceed via one-center, electrophilic coordination of the silyl group to hetero functional groups and exhibit unique selectivities.
- Noyori, R.,Murata, S.,Suzuki, M.
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p. 3899 - 3910
(2007/10/02)
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