- Reprint of: Impact of the corrin framework of vitamin B12 on the electrochemical carbon-skeleton rearrangement in comparison to an imine/oxime planar ligand; tuning selectivity in 1,2-migration of a functional group by controlling electrolysis potential
-
Among the coenzyme B12-dependent enzymes, methylmalonyl-CoA mutase (MMCM) catalyzes the carbon-skeleton rearrangement reaction between R-methylmalonyl-CoA and succinyl-CoA. Diethyl 2-bromomethyl-2-phenylmalonate, an alkyl bromide substrate having two different migrating groups (phenyl and carboxylic ester groups) on the β-carbon, was applied to the electrolysis mediated by a hydrophobic vitamin B12 model complex, heptamethyl cobyrinate perchlorate in this study. The electrolysis of the substrate at ? 1.0 V vs. Ag-AgCl by light irradiation afforded the simple reduced product (diethyl 2-methyl-2-phenylmalonate) and the phenyl migrated product (diethyl 2-benzyl-2-phenylmalonate), as well as the electrolysis of the substrate at ? 1.5 V vs. Ag-AgCl in the dark. The electrolysis of the substrate at ? 2.0 V vs. Ag-AgCl afforded the carboxylic ester migrated product (diethyl phenylsuccinate) as the major product. The selectivity for the migrating group was successfully tuned by controlling the electrolysis potential. We clarified that the cathodic chemistry of the Co(III) alkylated heptamethyl cobyrinate is critical for the selectivity of the migrating group through mechanistic investigations and comparisons to the simple vitamin B12 model complex, an imine/oxime-type cobalt complex.
- Abe, Masaaki,Hisaeda, Yoshio,Pan, Ling,Shimakoshi, Hisashi,Tahara, Keishiro,Yamaguchi, Ryoko
-
-
Read Online
- An aryne triggered ring-opening fluorination of cyclic thioethers with potassium fluoride
-
Herein, we report an aryne triggered ring-opening fluorination protocol of a great variety of saturated sulfur heterocycles. A key factor for the success is the identification of a suitable mediator. Compared to previous methods, this transition-metal free protocol employs low-cost potassium fluoride as the fluorine source. The operational simplicity and mild reaction conditions allow for the rapid synthesis of a wide range of aliphatic fluoride compounds in good yields.
- Fan, Rong,Liu, Binbin,Zheng, Tianyu,Xu, Kun,Tan, Chen,Zeng, Tianlong,Su, Shuaisong,Tan, Jiajing
-
supporting information
p. 7081 - 7084
(2018/07/05)
-
- Photocatalytic function of the B12 complex with the cyclometalated iridium(III) complex as a photosensitizer under visible light irradiation
-
A visible light induced three-component catalytic system with the cobalamin derivative (B12) as a catalyst, the cyclometalated iridium(iii) complex (Irdfppy, Irppy, Irpbt and [Ir{dF(CF3)ppy}2(dtbpy)]PF6) as a photosensitizer and triethanolamine as an electron source under N2 was developed. This catalytic system showed a much higher catalytic efficiency than the previous catalytic system using [Ru(ii)(bpy)3]Cl2 as the photosensitizer for the dechlorination reaction of 1,1-bis(4-chlorophenyl)-2,2,2-trichloroethane (DDT). Noteworthy is the fact that the remarkable high turnover number (over ten thousand) based on B12, which ranks at the top among the reported studies, was obtained when Irdfppy was used as a photosensitizer. This photocatalytic system was also successfully applied to the B12 enzyme-mimic reaction, i.e., the 1,2-migration of the phenyl group of 2-bromomethyl-2-phenylmalonate. The plausible reaction mechanism was proposed, which involved two quenching pathways, an oxidative quenching pathway and a reductive quenching pathway, to be responsible for the initial electron transfer of the excited-state photosensitizers during the DDT dechlorination reaction. Transient photoluminescence experiments revealed that the oxidative quenching of the photosensitizer dominated over the reductive quenching pathway.
- Tian, Hui,Shimakoshi, Hisashi,Park, Gyurim,Kim, Sinheui,You, Youngmin,Hisaeda, Yoshio
-
p. 675 - 683
(2018/02/16)
-
- Isomerization of olefins triggered by rhodium-catalyzed C-H bond activation: Control of endocyclic β-hydrogen elimination
-
Five-membered metallacycles are typically reluctant to undergo endocyclic β-hydrogen elimination. The rhodium-catalyzed isomerization of 4-pentenals into 3-pentenals occurs through this elementary step and cleavage of two C-H bonds, as supported by deuterium-labeling studies. The reaction proceeds without decarbonylation, leads to trans olefins exclusively, and tolerates other olefins normally prone to isomerization. Endocyclic β-hydrogen elimination can also be controlled in an enantiodivergent reaction on a racemic mixture.
- Yip, Stephanie Y. Y.,A?ssa, Christophe
-
supporting information
p. 6870 - 6873
(2015/06/02)
-
- Arylation with unsymmetrical diaryliodonium salts: A chemoselectivity study
-
Phenols, anilines, and malonates have been arylated under metal-free conditions with twelve aryl(phenyl)iodonium salts in a systematic chemoselectivity study. A new "anti-ortho effect" has been identified in the arylation of malonates. Several "dummy groups" have been found that give complete chemoselectivity in the transfer of the phenyl moiety, irrespective of the nucleophile. An aryl exchange in the diaryliodonium salts has been observed under certain arylation conditions. DFT calculations have been performed to investigate the reaction mechanism and to elucidate the origins of the observed selectivities. These results are expected to facilitate the design of chiral diaryliodonium salts and the development of catalytic arylation reactions that are based on these sustainable and metal-free reagents. Copyright
- Malmgren, Joel,Santoro, Stefano,Jalalian, Nazli,Himo, Fahmi,Olofsson, Berit
-
supporting information
p. 10334 - 10342
(2013/09/02)
-
- Congested C2-symmetric aryliodanes based on an anti-dimethanoanthracene backbone
-
A family of congested aryliodanes based on an anti-dimethanoanthracene backbone has been synthesised and two diaryliodonium salts and the iodyl derivative characterised by X-ray analysis. The latter shows a rare water coordination to the iodine(v) centre in the solid state. Applications of these reagents in functional group transfer reactions are reported. The Royal Society of Chemistry 2012.
- Murray, Stephen J.,Mueller-Bunz, Helge,Ibrahim, Hasim
-
supporting information; experimental part
p. 6268 - 6270
(2012/07/28)
-
- Electrochemical catalytic carbon-skeleton rearrangement mediated by imine/oxime-type B12 model complex
-
An electrochemical carbon-skeleton rearrangement of methylmalonate skeleton to succinate was successfully mediated by an imine/oxime-type cobalt complex using diethyl 2-bromomethyl-2- phenylmalonate as a model substrate of a coenzyme B12-dependent enzymatic reaction. Cyclic voltammetric and mass spectrometric studies revealed that this electrocatalysis of the alkyl bromide with 1,2-migration of a carboxylic ester group was achieved by the duet redox process between the reduction of the monoalkylated complex and the oxidation of the dialkylated complex.
- Tahara, Keishiro,Chen, Yi,Pan, Ling,Masuko, Takahiro,Shimakoshi, Hisashi,Hisaeda, Yoshio
-
p. 177 - 179
(2011/04/14)
-
- Preparation and reactivity of vitaminB12-TiO2 hybrid catalyst immobilized on a glass plate
-
The vitaminB12-TiO2 hybrid catalyst was effectively immobilized on a glass plate, and the immobilized catalyst shows an efficient reactivity for various molecular transformations, such as the 1,2-migration of a phenyl group and dechlorination of perchloroethylene during irradiation by UV light.
- Shimakoshi, Hisashi,Abiru, Makoto,Kuroiwa, Keita,Kimizuka, Nobuo,Watanabe, Midori,Hisaeda, Yoshio
-
experimental part
p. 170 - 172
(2010/05/15)
-
- Green molecular transformation by a B12-TiO2 hybrid catalyst as an alternative to tributyltin hydride
-
The B12-TiO2 hybrid catalyst was effectively used for the radical reactions, such as 1,2-migrations of phenyl groups and acyl groups under irradiation by UV light, and the selectivity of the reaction was controlled by the solvent system.
- Shimakoshi, Hisashi,Abiru, Makoto,Izumi, Shin-Ichiro,Hisaeda, Yoshio
-
scheme or table
p. 6427 - 6429
(2010/03/04)
-
- Unusual Tethering Effects in the Schmidt Reaction of Hydroxyalkyl Azides with Ketones: Cation-π and Steric Stabilization of a Pseudoaxial Phenyl Group
-
The Lewis acid-promoted reactions of chiral 2-aryl-3-azido-1-propanols with 4-substituted cyclohexanones lead to iminium ethers and ultimately caprolactams (following a hydrolysis step). In this study, it is shown that these reactions afford variable ratios of products, depending on the electronic nature of the phenyl group. These results are interpreted in the context of a cation?π stabilizing effect in the product-determining reaction intermediate. Remarkably, the best selectivity was obtained when an azidopropanol reagent containing a quaternary center was used; a control experiment showed that the high selectivity observed in this result depended upon the free rotation of the pseudoaxial aromatic group in the intermediate that affords the major product. Copyright
- Katz, Christopher E.,Aube, Jeffrey
-
p. 13948 - 13949
(2007/10/03)
-
- Novel photoreactions of 2-Aza-1,4-dienes in the triplet excited state and via radical-cation intermediates. 2-Aza-di-π-methane rearrangements yielding cyclopropylimines and N-vinylaziridines
-
Triplet-sensitized irradiation of 2-aza-1,4-dienes affords N-cyclopropylimines via 2-aza-di-π-methane (2-ADPM) rearrangement pathways. In the case of the pentaphenyl-substituted azadiene 1, irradiation leads to formation of cyclopropylimine 2 as well as N-vinylaziridine 3. The transformations represent the first examples of di-π-methane rearrangement reactions that yield three-membered heterocyclic products. SET-sensitized irradiation of 2-aza-1,4-dienes, by using 9,10-dicyanoanthracene (DCA) as an electron-acceptor sensitizer and biphenyl as cosensitizer, brings about regioselective formation of N-vinylaziridines. Under these conditions, azadiene 1 also affords cyclopropylimine 37, resulting from an aryl-di-π-methane rearrangement. This result demonstrates that di-π-methane reactions can also take place via radical-cation intermediates. In some instances, imine and olefin centered cation-radical intermediates, generated by SET-sensitized irradiation, undergo alternative reactions to produce isoquinoline and benzoazepine products.
- Armesto, Diego,Caballero, Olga,Ortiz, Maria J.,Agarrabeitia, Antonia R.,Martin-Fontecha, Mar,Torres, M. Rosario
-
p. 6661 - 6671
(2007/10/03)
-
- Palladium-catalyzed arylation of malonates and cyanoesters using sterically hindered trialkyl- and ferrocenyldialkylphosphine ligands
-
Palladium-catalyzed reactions of aryl bromides and chlorides with two common stabilized carbanions - enolates of dialkyl malonates and alkyl cyanoesters - are reported. An exploration of the scope of these reactions was conducted, and the processes were shown to occur in a general fashion. Using P(t-Bu)3 (1), the pentaphenylferrocenyl ligand (Ph5C5)Fe(C5H4)P(t-Bu) 2 (2), or the adamantyl ligand (1-Ad)P(t-Bu)2 (3), reactions of electron-poor and electron-rich, sterically hindered and unhindered aryl bromides and chlorides were shown to react with diethyl malonate, di-tertbutyl malonate, diethyl fluoromalonate, ethyl cyanoacetate, and ethyl phenylcyanoacetate. Although alkyl malonates and ethyl alkylcyanoacetates did not react with aryl halides using these catalysts, the same products were formed conveniently in one pot from diethylmalonate by cross-coupling of an aryl halide in the presence of excess base and subsequent alkylation.
- Beare, Neil A.,Hartwig, John F.
-
p. 541 - 555
(2007/10/03)
-
- Synthesis of 2-Substituted 2-Arylmalonates via Tricarbonylchromium Complexes
-
Tricarbonylchromium complexes 1 react with monosubstituted malonic acid esters 2 in DMSO at room temperature in the presence of KOtBu to give the complexes 3. After oxidative demetalation, the appropriate aryl derivatives 4 are obtained in moderate to good overall yields. Diastereoselective arylations of chirally modified malonates such as 5a-c were studied. The stereoselectivity was highest for the products 6c/6c′ (80:20) with (-)-8-phenylmenthol as alcohol component in the malonate 5.
- Deutsch,Bartoszek,Schneider,Zabel,Niclas
-
p. 261 - 265
(2007/10/03)
-
- Reactions of amino-substituted cyclodextrins with 2-arylpropanoic acid derivatives
-
Reactions of 6A-amino-6A-deoxy-β-cyclodextrin and 3A-amino-3A-deoxy-(2AS,3 AS)-β-cyclodextrin with the 3-nitrophenyl esters of 2-phenylpropanoic acid and Ibuprofen occur with only low diastereoselectivity, to afford the corresponding arylpropanamido-substituted cyclodextrins. These amides are also formed by decarboxylation of corresponding malonates, again with only low diastereoselectivity. The n.m.r. spectra of the amido-substituted cyclodextrins indicate that the aryl substituent is included within the cyclodextrin annulus at low temperature, but becomes dissociated from the cavity as the temperature is increased.
- Easton, Christopher J.,Lincoln, Stephen F.,May, Bruce L.,Papageorgiou, John
-
p. 451 - 456
(2007/10/03)
-