3968-85-2Relevant academic research and scientific papers
Effects of lipophilicity, protecting group and stereochemistry on the antimalarial activity of carbohydrate-derived thiochromans
Madumo, Gilbert K.,Moshapo, Paseka T.,Kinfe, Henok H.
, p. 817 - 833 (2018/01/10)
A series of novel carbohydrate-derived thiochromans has been successfully synthesized in order to investigate the influence of alkyl substituents on the aromatic ring of the thiophenol moiety in addition to the effect of protecting groups and stereochemistry on the sugar component of the target molecules. Results from the evaluation of the thiochromans for their antimalarial activity against the chloroquine-sensitive (3D7) strain of Plasmodium falciparum suggest that the presence of short chain alkyl substituents, a benzyl ether protecting group and equatorial orientation of the C-4 substituent on the sugar moiety are crucial structural features that impart high antimalarial activity.
Friedel-Crafts alkylation of benzene with 1,2-diphenyl-2-propanol, 1-chloro-2,3-diphenylpropane and 2-methyl-1-phenyl-2-butanol
Khalaf, Ali A.,Awad, Ibrahim M.,El-Emary,El-Aal, H.A.K. Abd
, p. 595 - 600 (2011/08/21)
The alkylation of benzene with 1,2-diphenyl-2-propanol (1) using AlCl 3/CH3NO2 catalyst gave a mixture of 1,2,2- (4) and 1,1,2-triphenylpropane (5) as product alkylates. With 85% H 2SO4 catalyst, the product consisted of E-1,2-diphenylpropene (6) after 2 h of a mixture of 5 and 6 after 18 h. Similar alkylation of benzene with 1-chloro-2,3-diphenylpropane (2) using AlCl 3 catalyst gave a mixture consisting of 4, 5 and 6. Finally, alkylation of benzene with 2-methyl-1-phenyl-2-butanol (3) using AlCl 3/CH3NO2 gave 2-methyl-1,1-diphenylbutane (10) as sole product alkylate. The identities of the products were confirmed spectroscopically and by comparison with unequivocally prepared samples. Mechanisms are proposed to rationalise the observed results.
Cobalt-catalyzed cross-coupling reactions of alkyl halides with allylic and benzylic grignard reagents and their application to tandem radical cyclization/cross-coupling reactions
Ohmiya, Hirohisa,Tsuji, Takashi,Yorimitsu, Hideki,Oshima, Koichiro
, p. 5640 - 5648 (2007/10/03)
Details of cobalt-catalyzed cross-coupling reactions of alkyl halides with allylic Grignard reagents are disclosed. A combination of cobalt(II) chloride and 1,2-bis(diphenylphosphino)ethane (DPPE) or 1,3-bis(diphenylphosphino)propane (DPPP) is suitable as a precatalyst and allows secondary and tertiary alkyl halides-as well as primary ones-to be employed as coupling partners for allyl Grignard reagents. The reaction offers a facile synthesis of quaternary carbon centers. which has practically never been possible with palladium, nickel, and copper catalysts. Benzyl, methallyl, and crotyl Grignard reagents can all couple with alkyl halides. The benzylation definitely requires DPPE or DPPP as a ligand. The reaction mechanism should include the generation of an alkyl radical from the parent alkyl halide. The mechanism can be interpreted in terms of a tandem radical cyclization/cross-coupling reaction. In addition, serendipitous tandem radical cyclization/cyclopropanation/carbonyl allylation of 5-alkoxy-6-halo-4-oxa-1-hexene derivatives is also described. The intermediacy of a carbon-centered radical results in the loss of the original stereochemistry of the parent alkyl halides, creating the potential for asymmetric cross-coupling of racemic alkyl halides.
NEW ACHIEVEMENTS IN THE USE OF ZIRCONIUM COMPLEXES IN THE CHEMISTRY OF ORGANO-ALUMINIUM AND MAGNESIUM COMPOUNDS
Dzhemilev, U. M.
, p. 4333 - 4346 (2007/10/02)
This paper describes some applications of a new reaction of catalytic cyclometallation of α-olefins, norbornenes and their derivatives, and 1,2-disubstituted acetylenes with organomagnesium and organoaluminium compounds effected by zirconium catalysts, leading to a series of five and macrocyclic heterocycles containing magnesium and aluminium.
Ionic hydrogenations of hindered olefins at low temperature. Hydride transfer reactions of transition metal hydrides
Bullock, R. Morris,Song, Jeong-Sup
, p. 8602 - 8612 (2007/10/02)
Sterically hindered olefins can be hydrogenated at -50 °C in dichloromethane using triflic acid (CF3SO3H) and a hydride donor. Mechanistic studies indicate that these reactions proceed by hydride transfer to the carbenium ion that is formed by protonation of the olefin. Olefins that form tertiary carbenium ions upon protonation are hydrogenated in high yields (90-100%). Styrenes generally produce lower yields of hydrogenated products (50-60%). Suitable hydride donors include HSiEt3 and several transition metal carbonyl hydrides (HW(CO)3Cp, HW(CO)3Cp*, HMo-(CO)3Cp, HMn(CO)5, HRe(CO)5, and HOs(CO)2Cp*; Cp = η-C5H5, Cp* = η5-C5Me5). A characteristic that is required for transition metal hydrides to be effective is that the cationic dihydrides (or dihydrogen complexes) that result from their protonation must have sufficient acidity to transfer a proton to the olefin, as well as sufficient thermal stability to avoid significant decomposition on the time scale of the hydrogenation reaction. Metal hydrides that fail due to insufficient stability of their protonated forms include HMo(CO)2(PPh3)Cp, HMo(CO)3Cp*, and HFe(CO)2Cp*. Other hydrides that fail are those that are protonated to give dihydrides or dihydrogen complexes that are not sufficiently acidic to protonate olefins, as found for HW(CO)2(PMe3)Cp and HRu(CO)(PMe3)Cp.
The reaction of benzotrihalides and benzal halides with magnesium. Synthetic and mechanistic studies
Ashby, E. C.,Al-Fekri, Dheya M.
, p. 275 - 292 (2007/10/02)
The benzotrihalides (PhCX3) where X = Cl, Br, and F were allowed to react with magnesium in THF at room temperature.When the halide was chloride or bromide, the trihalide gave diphenylacetylene in high yield in addition to several minor products which were identified.No reaction was observed when the halide was fluoride.When the corresponding dichloride was allowed to react with magnesium in THF, stilbene was formed as the major product.The possible mechanisms for these reactions are discussed.
On the Mechanism of the Reduction of Primary Halides with Grignard Reagents in the Presence of (dppf)PdCl2 or (dppf)Pd(0)
Yuan, Kaixu,Scott, William J.
, p. 6188 - 6194 (2007/10/02)
Reaction of primary alkyl halides with Grignard reagents in the presence (dppf)PdCl2 or (dppf)Pd(0) leads to reduction of the halide.The mechanism of the reduction is dependent on the solvent and the Grignard reagent.In tetrahydrofuran, reduction is independent of palladium.The alkyl halide is largely reduced by β-hydride transfer from the Grignard reagent.Competing with hydride transfer is a halogen-metal exchange reaction, which converts the alkyl halide into the corresponding Grignard reagent.Protonation of reaction mixture then gives the observed products.Grignard reagents that do not possess β-hydrogens undergo the halogen-metal exchange exclusively, but still lead to reduction of the alkyl halide.At subambient temperatures and in diethyl ether, reduction of primary alkyl halides with Grignard reagents in the absence of palladium catalysts is very slow.That reduction which does occur is almost exclusively the product of β-hydride transfer.The addition of (dppf)PdCl2 markedly accelerates the rate of reduction of alkyl halides in diethyl ether.The catalytic effect is proposed to occur through a catalytic cycle involving oxidative addition of the alkyl halide, hydride-transfer, and reductive-elimination steps.The order of the first two steps remains unclear.
Regioselective and Diastereoselective Alkyl-Alkene and Alkene-Alkene Coupling Promoted by Zirconocene and Hafnocene
Swanson, Douglas R.,Rousset, Christophe J.,Negishi, Ei-ichi,Takahashi, Tamotsu,Seki, Takashi,et al.
, p. 3521 - 3523 (2007/10/02)
The reaction of Cp2Zr(CH2CH2R1)2 with a monosubstituted terminal alkene (H2C=CHR2) can produce, in a highly regio- and diastereoselective manner, zirconacyclopentane derivatives; the trans-3,4-disubstituted derivatives may be formed to the extents of >98percent in cases where both R1 and R2 are alkyl, while the trans-2-aryl-4-alkyl derivatives may be formed to the extents of >98percent in the coupling between a monoalkyl-substituted olefin and styrene or its derivative.
