- Driving an equilibrium acetalization to completion in the presence of water
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Formation of an acetal from a carbonyl substrate by condensation with an alcohol is a classical reversible equilibrium reaction in which the water formed must be removed to drive the reaction to completion. A new method has been developed for acetalization of carbonyl substrates by diols in the presence of water. Complexation of poly(4-styrenesulfonic acid) with poly(4-vinylpyridine) generates a catalytic membrane of polymeric acid at the interface between two parallel laminar flows in a microchannel of a microflow reactor. The catalytic membrane provides a permeable barrier between the organic layer and water-containing layer in the reaction, and permits discharge of water to the outlet of the microreactor to complete the acetalization. Condensation of a variety of carbonyl substrates with diols proceeded in the presence of water in the microflow device to give the corresponding acetals in yields of up to 97% for residence times of 19 to 38 s. the Partner Organisations 2014.
- Minakawa, Maki,Yamada, Yoichi M. A.,Uozumi, Yasuhiro
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p. 36864 - 36867
(2014/11/08)
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- Stereoselective synthesis of tertiary ethers through geometric control of highly substituted oxocarbenium ions
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Fully substituted, fully controlled I The geometries of 1,1-disubstituted oxocarbenium ions and the conformations of oxocarbenium ions that contain a tertiary stereocenter can be predicted based on simple models. These models have been applied to highly stereoselective syntheses of tetrahydropyran derivatives that contain tertiary ethers (see scheme; RL, Rs, and RN represent large, small, and nucleophilic groups, respectively). (Figure Presented)
- Liu, Lei,Floreancig, Paul E.
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supporting information; experimental part
p. 5894 - 5897
(2010/12/18)
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- Chemoselective and chemospecific protection and deprotection of a carbonyl group using polystyrene divinylbenzene sulfonic acid
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Chemospecific protection of one carbonyl group of two identical carbonyls of 2,2-dialkyl-1,3-cyclohexanedione and chemoselective protection of aliphatic or aromatic carbonyls in the presence of conjugated carbonyl compounds using cross-linked polystyrene divinyl benzene sulfonic acid (SPS) as a heterogeneous catalyst has been demonstrated. Copyright
- Verma, Sanjeev K.,Sathe, Manisha,Kaushik
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experimental part
p. 1701 - 1707
(2010/07/15)
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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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- 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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- Photochemical Reaction of Benzene-1,2,4,5-tetracarbonitrile with the Ketals of Cyclic and Bicyclic Ketones
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The radical cations of the ethylene ketals of some cyclic and bicyclic ketones are generated by single electron transfer to excited benzene-1,2,4,5-tetracarbonitrile (TCB).Their fragmentation yields 1,5- and 1,6-distonic radical cations, which add to TCB(-.) to give alkyl>benzenetricarbonitriles.The reduction of the radical center occurs only to a small extent, and is enhanced in the presence of dodecylmercaptan, in the case of hindered radicals.The reaction of the camphor ethylene ketal (both alkylation of TCB and reduction) occurs with total diastereoselectivity at the reacting radical center.
- Mella, Mariella,Freccero, Mauro,Albini, Angelo
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p. 1047 - 1052
(2007/10/02)
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- Sulfonated charcoal, a mild and efficient reagent for the preparation of cyclic acetals, dithioacetals and benzodioxepines
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1,3-Dioxolanes, 1,3-Ditholanes and 1,5-dihydro-3H-2,4-benzodioxepines were prepared by the direct condensation of carbonyl compounds with 1,2-ethanediol, 1,2-ethanedithiol or 1,2-benzenedimethanol under the heterogeneous conditions of sulfonated charcoal catalyst.
- Patney, Haris K.
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p. 413 - 416
(2007/10/02)
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- N-(arylmethyl)-2-(or -4)-cyanopyridinium hexafluoroantimonates as new useful catalysts for acetalization of carbonyl compounds
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Carbonyl compounds 1 were converted to the corresponding 1,3-dioxolanes 2 and 1,3-dioxanes 4 with ethylene glycol and 2,2-dimethyl-1,3-propandiol, respectively, in the presence of 1-3 mol% of N-(benzyl, 4-methylbenzyl or 4-methoxybenzyl)-2(or -4)cyanopyridinium hexafluoroantimonates 3. The catalyst 3d was also effective for the tetrahydropyranylation.
- Lee,Lee,Takata,Endo
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p. 368 - 370
(2007/10/02)
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- The Conformational Behaviour of 10-Substituted Spirodecanes
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The conformational behaviour of 10-X-substituted 1,4-dioxa- and 1,4,6-trioxaspirodecanes 1-4 has been studied by 13C-, 19F- and 1H-NMR spectroscopy.Two X-ray analyses of (2a,e) are presented, and their implications to cleavage reactions of chiral acetals are discussed.Participation of twist boat forms in the conformeric equilibrium of at least 1c has been made plausible by observing 13C, 19F-NMR coupling constants.The ratios of axial to equatorial conformers in 1-4 have been calculated by molecular mechanics.
- Wolff, J. Jens,Frenking, Gernot,Harms, Klaus
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p. 551 - 561
(2007/10/02)
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- REGIO- AND STEREOSELECTIVE CONTROL IN THE ALKYLATION OF 1-ALKOXY-1,4-CYCLOHEXADIENES BY THE CHIRAL AUXILIARY APPROACH. ENANTIOSELECTIVE SYNTHESIS OF PRECURSORS FOR CIS-HYDRINDANES.
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A method is described for the regio- and diastereoselective alkylation of optically active 1-alkoxy-1,4-cyclohexadienes.Reaction conditions were optimised for substrates 4a with the per-O-methyl-β-D-glucopyranosyl group as chiral auxiliary.In the methylat
- Stanssens, Dirk,Keukeleire, Denis De,Vandewalle, Maurits
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p. 547 - 560
(2007/10/02)
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- Ring Expansions via Photoinduced Single Electron Transfer Promoted Opening of Cyclopropyl Ethers
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A general method of ring expansion involving acetal to ring-homologated acetal is described.The key steps in the overall process involve (a) acetal to enol ether conversion, (b) cyclopropane formation, and (c) photoinduced single electron transfer promoted opening of the cyclopropane.
- Gassman, Paul G.,Burns, Stephen J.
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p. 5576 - 5578
(2007/10/02)
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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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- 99.Transferts d'hydrogenes dans les cations radicaux ethylene-acetals derives de cyclopentanones et cyclohexanones
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Hydrogen Transfer during Decompositions of Molecular Ions of Acetals Derived from Substituted Cyclopentanones and Cyclohexanones.The isomerisation process of ethylene-acetal radical ions of low internal energy has been reinvestigated in more detail .The ring contraction of cyclohexane derivatives into methylcyclopentanes is quite general for these ions.The relative rates of H transfers to the C free resulting from C-C cleavage α to the acetal group plays the most important part in the mechanism.
- Audier, H. E.,Tabet, J. C.,Fetizon, M.
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p. 903 - 911
(2007/10/02)
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- ELECTROGENERATED ACID AS AN EFFICIENT CATALYST FOR ACETYLIZATION OF CARBONYL GROUP WITH 1,2-BISTRIMETHYLSILOXYETHANE
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Electrolysis of a mixture of carbonyl compounds and bistrimethylsiloxyethane in CH2Cl2-LiClO4-(Pt) readily gave the corresponding acetalized products in good yields.
- Torii, Sigeru,Inokuchi, Tsutomu
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p. 1349 - 1350
(2007/10/02)
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