Scandium trifluoromethaneslfonate, an efficient catalyst for the intermolecular carbonyl-ene reaction and the intramolecular cyclisation of citronellal

Aggarwal, Varinder K.; Vennall, G. P.; Davey, Paul N.; Newman, Chris

doi:10.1016/s0040-4039(98)00115-4

Cited by 69 publications

(37 citation statements)

References 12 publications

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“…If the acidic centers are very strong [6] it is necessary the work at low temperature to avoid aselective side reactions. Using a catalyst with an intermediate acidity, such as Beta, this is no longer a problem.…”

Section: The Effect Of the Reaction Conditionsmentioning

confidence: 99%

“…However, in this case, the catalyst is destroyed with NaOH after the reaction and cannot be recovered. Typical acid catalysts transform citronellal not only to the desired product, isopulegol, but also to the other three stereoisomers and other side products [4][5][6][7][8][9][10][11][12][13]. Most heterogeneous catalysts, such as hydrous zirconia [4], zeolites or mesoporous materials [5] do not allow to surpass the thermodynamic 75:25 equilibrium ratio of isopulegol:diastereoisomers.…”

Section: Introductionmentioning

confidence: 99%

“…With some homogeneous catalysts higher ratios have been reported, e.g. 94:6 for the Sc(OTf) 3 catalyst [6], or 79:21 for the Bi(OTf) 3 catalyst [7]. Milone et al [8] reported a 86% selectivity for (-)-isopulegol with a SiO 2 -supported ZnBr 2 catalyst, but the amount of Zn was very high (14% wt%) and the use of ZnBr 2 is not environmentally friendly.…”

Section: Introductionmentioning

confidence: 99%

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Heterogeneous Catalytic Transformation of Citronellal to Menthol in a Single Step on Ir-Beta Zeolite Catalysts

et al. 2009

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The synthesis of menthol from citronellal was studied on bifunctional Ir/Beta zeolite catalysts, prepared via impregnation of Beta zeolite with different concentrations of Ir. The results show that Beta zeolites, impregnated with Ir, catalyze the one-pot full conversion of citronellal to menthol by consecutive acid-catalyzed cyclization and Ir-catalyzed hydrogenation. The best results (95% selectivity for the menthol isomers, of which 75% is the desired (±)-menthol) were recorded on 3% Ir/Beta zeolite catalyst. In contrast with earlier studies, 0.05 g Ir/Beta catalyst per mL of substrate leads to complete and selective substrate transformation. The textural properties, acidity and hydrogenation function were studied by liquid N 2 adsorption-desorption, FT-IR, XPS and hydrogen chemisorption techniques. To clarify the mechanism of the cyclization of citronellal, tests were also performed using zeolites with different acidity and loaded with other metals (Pt, Pd, Rh, Ru).

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Section: The Effect Of the Reaction Conditionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Heterogeneous Catalytic Transformation of Citronellal to Menthol in a Single Step on Ir-Beta Zeolite Catalysts

et al. 2009

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“…In this respect, a great number of Lewis acids have been found to promote this cyclization. Good selectivities favoring isopulegol can be achieved with zinc salts (ZnBr 2 and ZnI 2 ), 4 although in stoichiometric amounts, and catalytic scandium triflate, 6 whereas neoisopulegol is slightly favored using SbCl 5 4 or molybdenum(II) and tungsten(II) catalysts. 7 We wish to report that citronellal undergoes cyclization in the presence of catalytic amounts of NbCl 5 , TaCl 5 and InCl 3 .…”

Section: Introductionmentioning

confidence: 99%

Intramolecular ene reactions catalyzed by NbCl5, TaCl5 and InCl3

Andrade¹,

Vercillo²,

Rodrigues³

et al. 2004

J. Braz. Chem. Soc.

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Niobium pentachloride, tantalum pentachloride and indium trichloride efficiently catalysed the cyclization of (R)-citronellal to a mixture of isopulegol and neoisopulegol in good yields. A comparative study was carried out which demonstrated that NbCl 5 is the most active Lewis acid whereas InCl 3 is the most selective one. The selectivity of the reactions varied according to the Lewis acid used and to the solvent. The ene reaction of a 1,7-diene was also investigated. In this case, all Lewis acids tested showed excellent selectivity.

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“…From the results of these negative control experiments, we suggest that compound 7 occurs via a reaction related to a carbonylene reaction between the o-quinonemethide intermediate 3 and 2-methylpropene followed by a methanol addition on the resulting double bond. Carbonyl-ene reactions catalysed by lanthanide triflate have been reported [13,14] and an example of a competition between this reaction and a Diels-Alder cycloaddition was also observed [13]. An excellent review describes all the reactions that can be catalysed by lanthanides triflates [15].…”

mentioning

confidence: 99%

A simple two steps ytterbium triflate‐catalysed preparation of 2,2‐dimethyl‐2h‐chromenes from salicylaldehydes and 2‐methylpropene

Prado

Janin

Bost

2006

Journal of Heterocyclic Chem

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The preparation of various 2,2-dimethyl-2H-chromenes was achieved in two steps via an ytterbium triflate-catalysed reaction between salicylaldehydes, trimethylorthoformate and 2-methylpropene. From salicylaldehyde, two reaction products were characterised: 4-methoxy-2,2-dimethylchroman and 2-(1,3-dimethoxy-3-methylbutyl)phenol. The former compound probably results from a Lewis acid-catalysed [2+4] cycloaddition between the intermediate quinonemethide and 2-methylpropene whereas the latter may occur via a reaction related to a carbonyl-ene reaction between the quinonemethide and 2-methylpropene. Both compounds were subjected to a catalytic acidic treatment leading to 2,2-dimethyl-2H-chromene. Starting from various salicylaldehydes, the scope of this method was investigated.J. Heterocyclic Chem., 43, 1605Chem., 43, (2006.In the course of synthesis of biologically active chromene derivatives, [1] our attention was drawn [2] to a patent [3] reporting a simple preparation of 2,2-dimethyl-2H-chromene (2) using a reaction between salicylaldehyde (1) and 2-methylpropene catalysed by acidic silicaalumina catalysts at 150 °C or zinc chloride at 75°C. More recently [4], the preparation of furo[2,3-b]benzopyran 5 was achieved in excellent yield using the ytterbium triflate-catalysed reaction between salicylaldehyde (1), trimethylorthoformate and dihydrofuran 4. As illustrated in Scheme 1, this reaction is an example [5][6][7][8][9][10][11] We wish to report here the synthesis of various 2,2-dimethylchromenes via an ytterbium triflate-catalysed reaction between salicylaldehydes, trimethylorthoformate and 2-methylpropene.From the overnight reaction between salicylaldehyde (1), trimethylorthoformate, 2-methylpropene and ytterbium triflate in a sealed flask at room temperature, we could isolate and characterise compounds 6 and 7 in 27 and 14% yield respectively. In a control experiment, compound 6 was subjected to the reaction conditions but no ring opening into 7 took place. Moreover, from salicylaldehyde (1), no reaction was seen if trimethylorthoformate was omitted. From the results of these negative control experiments, we suggest that compound 7 occurs via a reaction related to a carbonylene reaction between the o-quinonemethide intermediate 3 and 2-methylpropene followed by a methanol addition on the resulting double bond. Carbonyl-ene reactions catalysed by lanthanide triflate have been reported [13,14] and an example of a competition between this reaction and a Diels-Alder cycloaddition was also observed [13]. An excellent review describes all the reactions that can be catalysed by lanthanides triflates [15]. As related intramolecular cycloadditions have been reported previously [9], including an iodine-catalysed example [10], we also tried iodine on our substrates but without success. In order to obtain the corresponding chromene, compounds 6 and 7 were heated to reflux in toluene in the presence of a catalytic amount of p-toluenesulfonic acid (PTSA). It is noteworthy that allowing the resulting methanol to distil fr...

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Scandium trifluoromethaneslfonate, an efficient catalyst for the intermolecular carbonyl-ene reaction and the intramolecular cyclisation of citronellal

Cited by 69 publications

References 12 publications

Heterogeneous Catalytic Transformation of Citronellal to Menthol in a Single Step on Ir-Beta Zeolite Catalysts

Heterogeneous Catalytic Transformation of Citronellal to Menthol in a Single Step on Ir-Beta Zeolite Catalysts

Intramolecular ene reactions catalyzed by NbCl5, TaCl5 and InCl3

A simple two steps ytterbium triflate‐catalysed preparation of 2,2‐dimethyl‐2h‐chromenes from salicylaldehydes and 2‐methylpropene

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