- Iron(II) and Copper(I) Control the Total Regioselectivity in the Hydrobromination of Alkenes
-
A new method that allows the complete control of the regioselectivity of the hydrobromination reaction of alkenes is described. Herein, we report a radical procedure with TMSBr and oxygen as common reagents, where the formation of the anti-Markovnikov product occurs in the presence of parts per million amounts of the Cu(I) species and the formation of the Markovnikov product occurs in the presence of 30 mol % iron(II) bromide. Density functional theory calculations combined with Fukui's radical susceptibilities support the obtained results.
- Cruz, Daniel A.,Sinka, Victoria,De Armas, Pedro,Steingruber, Hugo Sebastian,Fernández, Israel,Martín, Víctor S.,Miranda, Pedro O.,Padrón, Juan I.
-
supporting information
p. 6105 - 6109
(2021/08/18)
-
- Visible Light-Mediated Conversion of Alcohols to Bromides by a Benzothiadiazole-Containing Organic Photocatalyst
-
The search for metal-free, stable and high effective photocatalysts with sufficient photo-redox potentials remains a key challenge for organic chemists. Here, we present a benzothiadiazole-containing molecular organic photocatalyst with redox potentials of ?1.30 V and +1.64 V vs. SCE. The singlet state lifetime is 13 ns. Direct conversion from aliphatic alcohols to bromides has been conducted with the designed organic photocatalyst under visible light irradiation with high efficiency and selectivity. The catalytic efficiency of the novel benzothiadiazole-based photocatalyst is comparable with the state-of-art metal and non-metal catalysts. Furthermore, advanced photophysical studies including time-resolved photoluminescence and transient absorption spectroscopy offer a powerful support for photo-induced electron transfer from photocatalyst to the reactive substrates. Lastly, no photo-bleaching effect is observed, demonstrating the high stability and recyclable of the designed organic photocatalyst. (Figure presented.).
- Li, Run,Gehrig, Dominik W.,Ramanan, Charusheela,Blom, Paul W. M.,Kohl, Fabien F.,Wagner, Manfred,Landfester, Katharina,Zhang, Kai A. I.
-
p. 3852 - 3859
(2019/07/15)
-
- Enantiospecific Solvolytic Functionalization of Bromochlorides
-
Herein, we report that under mild solvolytic conditions, enantioenriched bromochlorides can be ionized, stereospecifically cyclized to an array of complex bromocyclic scaffolds, or intermolecularly trapped by exogenous nucleophiles. Mechanistic investigations support an ionic mechanism wherein the bromochloride serves as an enantioenriched bromonium surrogate. Several natural product-relevant motifs are accessed in enantioenriched form for the first time with high levels of stereocontrol, and this technology is applied to the scalable synthesis of a polycyclic brominated natural product. Arrays of nucleophiles including olefins, alkynes, heterocycles, and epoxides are competent traps in the bromonium-induced cyclizations, leading to the formation of enantioenriched mono-, bi-, and tricyclic products. This strategy is further amenable to intermolecular coupling between cinnamyl bromochlorides and a diverse set of commercially available nucleophiles. Collectively, this work demonstrates that enantioenriched bromonium chlorides are configurationally stable under solvolytic conditions in the presence of a variety of functional groups.
- Burckle, Alexander J.,Gál, Bálint,Seidl, Frederick J.,Vasilev, Vasil H.,Burns, Noah Z.
-
supporting information
p. 13562 - 13569
(2017/10/05)
-
- HBr–DMPU: The First Aprotic Organic Solution of Hydrogen Bromide
-
HBr and DMPU (1,3-dimethyl-3,4,5,6-tetrahydro-2-pyrimidinone) form a room-temperature-stable complex that provides a mild, effective, and selective hydrobrominating reagent toward alkynes, alkenes, and allenes. HBr–DMPU could also replace other halogenating reagents in the halo-Prins reaction, ether cleavage, and deoxy-bromination reactions.
- Li, Zhou,Ebule, Rene,Kostyo, Jessica,Hammond, Gerald B.,Xu, Bo
-
supporting information
p. 12739 - 12743
(2017/09/25)
-
- A facile and green protocol for nucleophilic substitution reactions of sulfonate esters by recyclable ionic liquids [bmim][X]
-
Ionic liquids [bmim][X] (X = Cl, Br, I, OAc, SCN) are highly efficient reagents for nucleophilic substitution reactions of sulfonate esters derived from primary and secondary alcohols. The counter anions (X-) of the ionic liquids, [bmim][X], effectively replace the sufonates affording the corresponding substitution products such as alkyl halides, acetates, and thiocyanides in excellent yields. The newly developed protocol is very environmentally attractive because the reactions use stoichiometric amounts of ionic liquids as sole reagents in most cases and do not require additional solvents, any other activating reagents, non-conventional equipment, or special precautions. Moreover, these ionic liquids can be readily recycled without loss of reactivity, making the whole process greener.
- Liu, Yajun,Xu, Yongnan,Jung, Sun Ho,Chae, Junghyun
-
p. 2692 - 2698,7
(2012/12/12)
-
- A facile and green protocol for nucleophilic substitution reactions of sulfonate esters by recyclable ionic liquids [bmim][X]
-
Ionic liquids [bmim][X] (X = Cl, Br, I, OAc, SCN) are highly efficient reagents for nucleophilic substitution reactions of sulfonate esters derived from primary and secondary alcohols. The counter anions (X-) of the ionic liquids, [bmim][X], effectively replace the sufonates affording the corresponding substitution products such as alkyl halides, acetates, and thiocyanides in excellent yields. The newly developed protocol is very environmentally attractive because the reactions use stoichiometric amounts of ionic liquids as sole reagents in most cases and do not require additional solvents, any other activating reagents, non-conventional equipment, or special precautions. Moreover, these ionic liquids can be readily recycled without loss of reactivity, making the whole process greener. Georg Thieme Verlag KG Stuttgart · New York.
- Liu, Yajun,Xu, Yongnan,Jung, Sun Ho,Chae, Junghyun
-
p. 2692 - 2698
(2013/01/15)
-
- Alkylboronic esters from palladium- and nickel-catalyzed borylation of primary and secondary alkyl bromides
-
Palladium- and nickel-catalyzed cross-coupling recations of unactivated alkyl bromides with diboron reagents have been developed as practical methods for the synthesis of primary and secondary alkylboronic esters. These reactions extend the concept and utility of Pd- and Ni-catalyzed cross-coupling of aliphatic electrophiles. They also show different substrate selectivity and ligand dependence as compared to the recently reported Cu-catalyzed borylation reaction. Copyright
- Yi, Jun,Liu, Jin-Hui,Liang, Jun,Dai, Jian-Jun,Yang, Chu-Ting,Fu, Yao,Liu, Lei
-
supporting information; experimental part
p. 1685 - 1691
(2012/07/28)
-
- Iron(III)-catalyzed halogenations by substitution of sulfonate esters
-
A novel halogenation reaction from sulfonates catalyzed by iron(III) is described. The reaction can be performed as a stoichiometric or a catalytic version. This reaction provides a convenient strategy for the efficient access to structurally diverse secondary chlorides, bromides and iodides. The stereochemical course of the reaction is governed by the substrate and the experimental conditions. Secondary alcohols modified as quisylates or pysylates are substantially more reactive. Aliphatic quisylates proceed with overall inversion of configuration under catalytic conditions. Chemoselectivity in bismesylates was observed in favour of the secondary mesylate. Additionally, based on the experimental results, a possible catalytic cycle for the halogenation has been proposed.
- Ortega, Nuria,Feher-Voelger, Andres,Brovetto, Margarita,Padron, Juan I.,Martin, Victor S.,Martin, Tomas
-
p. 963 - 972
(2011/06/20)
-
- Enantioselectivity of haloalkane dehalogenases and its modulation by surface loop engineering
-
In the loop: Engineering of the surface loop in haloalkane dehalogenases affects their enantiodiscrimination behavior. The temperature dependence of the enantioselectivity (lnE versus 1/T) of β-bromoalkanes by haloalkane dehalogenases is reversed (red data points) by deletion of the surface loop; the selectivity switches back when an additional single-point mutation is made. This behavior is not observed for -bromoesters.
- Prokop, Zbynek,Sato, Yukari,Brezovsky, Jan,Mozga, Tomas,Chaloupkova, Radka,Koudelakova, Tana,Jerabek, Petr,Stepankova, Veronika,Natsume, Ryo,Van Leeuwen, Jan G. E.,Janssen, Dick B.,Florian, Jan,Nagata, Yuji,Senda, Toshiya,Damborsky, Jiri
-
supporting information; experimental part
p. 6111 - 6115
(2010/11/05)
-
- NUCLEOPHILE ASSISTING LEAVING GROUPS
-
Sulfonate leaving groups include a cation chelating moiety, e.g. a polyether or crown ether. The chelating moiety stabilizes the sulfonate leaving group by forming a complex with a cation of a cation-nucleophile combination. The stabilized leaving group is more easily displaced under many conditions than are standard arylsulfonate leaving groups such as the toxyl group. The chelating moiety also favors certain cations depending on the identity of the moiety thereby enhancing the reaction rate with nucleophilic salts containing the preferred cation. Use of the inventive leaving groups results in improved yields, decreased reaction times and improved product purity.
- -
-
Page/Page column 15-16
(2010/11/08)
-
- Arylsulfonate-based nucleophile assisting leaving groups
-
The synthesis and unique reactivity of a series of arylsulfonate-based nucleophile assisting leaving groups (NALG) containing oligomeric ether units (including crown ethers) attached to the arylsulfonyl ring in the ortho orientation are described. The reactions of a variety of these ether-containing alkyl sulfonates with metal halides proceeded at substantially greater rates than electronically similar sulfonates. These ether-containing leaving groups also displayed marked selectivity for lithium halides relative to the corresponding sodium and potassium salts in nucleophilic displacement reactions.
- Lepore, Salvatore D.,Bhunia, Anjan K.,Cohn, Pamela
-
p. 8117 - 8121
(2007/10/03)
-
- A new supported reagent for the photochemical generation of radicals in solution
-
matrix presented A new polymer-supported radical source was developed by loading an N-hydroxy thiazole 2(3)-thione on a Wang resin. This new supported reagent can be employed for a solid-phase version of the Hunsdiecker reaction or to liberate free alkoxy radicals, in a variant of the "catch and release" technique, under very mild conditions (irradiation with a discharge lamp) and simplifying the purification procedure.
- De Luca, Lidia,Giacomelli, Giampaolo,Porcu, Giancarlo,Taddei, Maurizio
-
p. 855 - 857
(2007/10/03)
-
- Nucleophilic substitution of 1-phenyl-2-phenyl telluropropane to yield 2-halo-1-phenylpropanes
-
Mechanism of a novel transformation of the alkyl phenyltellurides to alkyl halides via nucleophilic substitution of the phenyltelluro group in organotelluriums is studied on the basis of kinetics and stereochemistry using the titled chiral substrate. The results obtained strongly suggest that the substitutions proceed via SN2 mechanism with Walden inversion and very low Arrhenius' energies of activation.
- Ogura, Fumio,Okada, Yoshiharu,Nishimura, Naoko,Hamamoto, Kenichiro,Miyakawa, Makoto,Otsubo, Tetsuo,Aso, Yoshio,Inoue, Shinobu,Tsutsui, Koji
-
p. 203 - 210
(2007/10/03)
-
- Syntheses of (+/-)-Deoxyschizandrin and the Lignan, 1,4-Bis(3,4-dimethoxyphenyl)-2,3-dimethylbutane
-
(+/-)-Deoxyschizandrin (1) has been synthesised through a dimerisation reaction as a key step.The Grignard reagent from 1-(3,4,5-trimethoxyphenyl)-2-bromopropane (10) on reaction with 2-t-butyl-3-phenyloxaziridine gives 1,4-bis(3,4,5-trimethoxyphenyl)-2,3-dimethylbutane (11), which is cyclised using vanadium oxytrifluoride to get deoxyschizandrin (1).Following the above methodology, 1,4-bis(3,4-dimethoxyphenyl)-2,3-dimethylbutane (2), a lignan has also been prepared.
- Gunasekaran, A.,Balasubramanian, K.
-
p. 308 - 310
(2007/10/02)
-
- ALKYLATION OF AROMATIC HYDROCARBONS WITH ALLYL BROMIDE IN THE PRESENCE OF SOME LEWIS ACIDS'
-
The alkylation of benzene, toluene, and ethyl- and isopropylbenzenes with allyl bromide in the presence of FeCl3.2.5H2O, FeBr3.3.5H2O, ZnCl2/Al2O3, and ZnBr2/Al2O3 is fairly selective and leads mainly to the formation of 1-aryl-2-bromopropanes with yields of 54-80percent.
- Magerramov, M. N.
-
p. 115 - 118
(2007/10/02)
-
