- Construction of Distant Stereocenters by Enantioselective Desymmetrizing Carbonyl-Ene Reaction
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An efficient desymmetrizing carbonyl-ene reaction of 1-substituted 4-methylenecyclohexanes with glyoxal derivatives was thus executed by a chiral N,N′-dioxide/NiII catalyst, providing facile access to cyclohexene derivatives bearing two remote 1,6-related stereocenters. This distal stereocontrol methodology originates from the efficient interaction between the catalyst with enophiles, discrimination of the two chair conformations of olefinic components, and the intrinsic six-membered transition-state structure of ene process.
- Luo, Weiwei,Lin, Lili,Zhang, Yu,Liu, Xiaohua,Feng, Xiaoming
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p. 3374 - 3377
(2017/07/15)
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- A remarkable iodine-catalyzed protection of carbonyl compounds
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We report here a remarkably simple molecular iodine-catalyzed protection method for various carbonyl compounds as ketals in a general reaction. The iodine-catalyzed reaction of mandelic acid and lactic acid with several aldehydes has furnished a highly diastereoselective synthesis of cis and trans dioxolanones.
- Banik, Bimal K.,Chapa, Marin,Marquez, Jocabed,Cardona, Magda
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p. 2341 - 2343
(2007/10/03)
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- Acidic properties of sulfonic acid-functionalized FSM-16 mesoporous silica and its catalytic efficiency for acetalization of carbonyl compounds
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Propyl-sulfonic acid-functionalized FSM-16 mesoporous silica (SO 3H-FSM) is prepared by a conventional post-modification method. For the acetalization of carbonyl compounds with ethylene glycol, SO 3H-FSM shows a higher rate and 1,3-dioxolane yield than conventional heterogeneous solid acids such as zeolites, montmorillonite K10 clay, silica-alumina, and the sulfonic resin. SO3H-FSM is stable during the reaction, with no leaching and deactivation of sulfonic acid groups, and is reusable without loss of its activity. The acidity and hydrophilicity of SO 3H-FSM are well characterized by the microcalorimetry of NH 3 adsorption, NH3-TPD, and H2O-TPD, and the result is compared with those for various aluminosilicate zeolites (HZSM5, HBEA, HY) and K10 clay. It is found that NH3-TPD is not suitable for characterizing the acidity of SO3H-FSM, because the decomposition of SO3H groups on SO3H-FSM begins above 200°C. An NH 3 adsorption microcalorimetric experiment at 150°C shows that, compared with HZSM5, SO3H-FSM has a smaller number of acid sites but has a similar number of strong acid sites with ammonia adsorption heat above 140 kJ mol-1. Comparison of the structural properties and catalytic results shows that a large pore diameter and low hydrophilicity are required to obtain high activity. Bronsted acid sites with a relatively strong acid strength are more suitable for this reaction, but the high acid concentration is not indispensable. The high activity of SO3H-FSM should be caused by the presence of the strong Bronsted acid sites in the mesopore with a relatively low hydrophilicity, where both reactants can smoothly access the acid sites.
- Shimizu, Ken-Ichi,Hayashi, Eidai,Hatamachi, Tsuyoshi,Kodama, Tatsuya,Higuchi, Tomoya,Satsuma, Atsushi,Kitayama, Yoshie
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p. 131 - 138
(2007/10/03)
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- I2-mediated photochemical preparation of 2-substituted 1,3-dioxolanes and tetrahydrofurans from alcohols with polymer-supported hypervalent iodine reagent, PSDIB
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Various 2-substituted 1,3-dioxolanes, 1,3-dioxanes, and tetrahydrofurans were obtained selectively in good to moderate yields from the corresponding alcohols with PSDIB in the presence of iodine under irradiation conditions. Moreover, PSDIB was repeatedly used for the same reactions keeping good yield of the cyclic product.
- Teduka, Tomomasa,Togo, Hideo
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p. 923 - 926
(2007/10/03)
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- An efficient procedure for the preparation of cyclic ketals and thioketals catalyzed by zirconium sulfophenyl phosphonate
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A convenient method for the preparation of cyclic ketals and thioketals using zirconium sulfophenyl phosphonate as catalyst is described.
- Curini,Epifano,Marcotullio,Rosati
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p. 1182 - 1184
(2007/10/03)
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- 1,3-Dioxolanes from carbonyl compounds over zeolite HSZ-360 as a reusable, heterogeneous catalyst
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Carbonyl compounds are converted, in good yields, into their 1,3-dioxolanes over zeolite HSZ-360, as a new reusable catalyst. Good chemoselectivity is also observed.
- Ballini, Roberto,Bosica, Giovanna,Frullanti, Bettina,Maggi, Raimondo,Sartori, Giovanni,Schroer, Frank
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p. 1615 - 1618
(2007/10/03)
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- A New Ready, High-Yielding, General Procedure for Acetalization of Carbonyl Compounds
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Carbonyl compounds are smoothly and rapidly acetalized by treatment with alcohols, in anhydrous acetonitrile, in the presence of polystyryl diphenyl phosphine - iodine complex as catalyst.Open and cyclic acetals, including 1,3-dioxolanes, 1,3-oxathiolanes, and 1,3-dithiolanes, of miscellaneous aldehydes and ketones have been successfully prepared in this way.The isolation of the product is very easily performed, by simple filtration of the polymer-linked phosphine oxide which is formed in the reaction.
- Caputo, Romualdo,Ferreri, Carla,Palumbo, Giovanni
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p. 386 - 389
(2007/10/02)
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