- Ketalization of ketones to 1,3-dioxolanes and concurring self-aldolization catalyzed by an amorphous, hydrophilic SiO2-SO3H catalyst under microwave irradiation
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The amorphous, mesoporous SiO2-SO3H catalyst with a surface area of 115 m2 g-1 and 1.32 mmol H+ per g was very efficient for the protonation of ketones on a 10percent (m/m) basis, and the catalyst-bound intermediates can be trapped by polyalcohols to produce ketals in high yields or suffer aldol condensations within minutes under low-power microwave irradiation. The same catalyst can easily reverse the ketalization reaction. Printed in Brazil-
- Barbosa, Sandro L.,Ottone, Myrlene,De Almeida, Mainara T.,Lage, Guilherme L.C.,Almeida, Melina A.R.,Nelson, David Lee,Dos Santos, Wallans T.P.,Clososki, Giuliano C.,Lopes, Norberto P.,Klein, Stanlei I.,Zanatta, Lucas D.
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p. 1663 - 1671
(2018/06/29)
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- 3,3,9,9-Tetramethyl-1,5,7,11-tetraoxaspiro[5.5]undecane as a reagent for protection of carbonyl compounds
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3,3,9,9-Tetramethyl-1,5,7,11-tetraoxaspiro[5.5]undecane is introduced as a new, stable and chemoselective reagent for the protection of aldehydes and ketones under mild reaction condition in high yield.
- Rahimizadeh, Mohammad,Bakavoli, Mehdi,Shiri, Ali,Eshghi, Hossein,Saberi, Sattar
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experimental part
p. 704 - 706
(2009/09/25)
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- Indium(III)trifluoromethanesulfonate as a mild, efficient catalyst for the formation of acetals and ketals in the presence of acid sensitive functional groups
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Aldehydes and ketones, including acetophenone and benzophenone, are readily protected under mild, neutral conditions in the presence of various alcohols or orthoformates and catalytic amounts of indium(III) trifluoromethanesulfonate (0.8 mol %) under either room temperature or mild heating conditions to give the corresponding cyclic and acyclic acetals and ketals in good to excellent yields. Acid sensitive functional groups, N-Boc, THP, and TBDMS do not undergo competitive deprotection under the reported conditions.
- Gregg, Brian T.,Golden, Kathryn C.,Quinn, John F.
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p. 3287 - 3295
(2008/09/21)
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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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