Synthesis of ionones on solid Br?nsted acid catalysts: Effect of acid site strength on ionone isomer selectivity
The effect of Br?nsted acid site strength on the liquid-phase conversion of pseudoionone to ionone isomers (α-, β- and γ-ionone) was studied on resin Amberlyst 35W, silica-supported heteropolyacid (HPAS) and silica-supported triflic acid (TFAS). Catalyst acidity was probed by temperature-programmed desorption of NH3 coupled with infrared spectra of adsorbed pyridine. The initial pseudoionone conversion rate followed the order: TFAS > Amberlyst 35W ≈ HPAS. Synthesis of the three ionone isomers occurred via a common cyclic carbocation intermediate formed from the activation of the pseudoionone molecule on Br?nsted acid sites. Initial ionone mixtures containing a α:β:γ isomer distribution of about 40:20:40 were formed, irrespective of the acid site strength. But the ionone mixture composition changed with the progress of the reaction because γ-ionone was consecutively converted to α-ionone on HPAS and Amberlyst 35W, whereas the stronger acid sites of TFAS converted γ-ionone to β-ionone.
Díez,Apesteguía,Di Cosimo
scheme or table
p. 267 - 274
(2010/11/19)
Supported choline hydroxide (ionic liquid) as heterogeneous catalyst for aldol condensation reactions
Choline hydroxide was used as a basic catalyst for aldol condensation reactions to produce new C-C bonds between several ketones and aldehydes. Choline supported on MgO exhibits higher TOF values than other well known basic catalysts in these reactions.
Abello, Sonia,Medina, Francisco,Rodriguez, Xavier,Cesteros, Yolanda,Salagre, Pilar,Sueiras, Jesus E.,Tichit, Didier,Coq, Bernard
p. 1096 - 1097
(2007/10/03)
Polyvinylogation Reagents: 1-Lithio-4-trimethylsiloxy-penta-1,3-diene and 1-Lithio-4-ethoxy-2-methyl-buta-1,3-diene
Title products, lithiodienol ethers 6a and 7a, synthetic equivalents of 4-lithio pent-3-ene-2-one and 4-lithio-senecialdehyde were obtained by bromine-lithium exchange.They are choice reagents for the transformations 1 -> 2 and 1 -> 3, respectively.
Duhamel, Lucette,Ancel, Jean-Erick
p. 9237 - 9250
(2007/10/02)
Wittig-Horner Reactions in Heterogeneous Media; 2. A Convenient Synthesis of α,β-Unsaturated Esters and Ketones using Weak Bases in Water
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Villieras, Jean,Rambaud, Monique
p. 300 - 303
(2007/10/02)
Novel synthesis of dienones and enones from propargyl alcohols and allyl alcohols with 2,2 dimethoxypropane: synthesis of ionone and irone
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Ishihara,Kitahara,Matsui
p. 439 - 442
(2007/10/12)
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