Comparison of AlEt2Cl and ZnCl2 supported on silica gel as catalysts of Diels-Alder reactions. Influence of the nature of the dienophile

Garcı́a, José I.; Mayoral, J. A.; Pires, Elísabet; Brown, David R.; Massam, Jarrod

doi:10.1007/bf00807764

Cited by 11 publications

(6 citation statements)

References 15 publications

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“…As reported previously [80], Zn(Si) is a better catalyst than Al(Si) or Ti(Si) for Diels-Alder reactions involving , -unsaturated nitriles such as acrylonitrile, and good yields of the corresponding cycloadducts were obtained with this catalyst. As reported previously [80], Zn(Si) is a better catalyst than Al(Si) or Ti(Si) for Diels-Alder reactions involving , -unsaturated nitriles such as acrylonitrile, and good yields of the corresponding cycloadducts were obtained with this catalyst.…”

Section: Diels-alder Reactions Of Furanssupporting

confidence: 72%

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Microwave-Assisted Reactions in Heterocyclic Compounds with Applications in Medicinal and Supramolecular Chemistry

Hoz¹,

Díaz‐Ortiz²,

Moreno³

et al. 2007

CCHTS

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Microwave irradiation has been successfully applied in organic chemistry. Spectacular accelerations, higher yields under milder reaction conditions and higher product purities have all been reported. Indeed, a number of authors have described success in reactions that do not occur under conventional heating and modifications in selectivity (chemo-, regio- and stereoselectivity) have even been reported. Recent advances in microwave-assisted combinatorial chemistry include high-speed solid-phase and polymer-supported organic synthesis, rapid parallel synthesis of compound libraries, and library generation by automated sequential microwave irradiation. In addition, new instrumentation for high-throughput microwave-assisted synthesis continues to be developed at a steady pace. The impressive speed combined with the unmatched control over reaction parameters justifies the growing interest in this application of microwave heating. In this review we highlight our recent advances in this area, with a particular emphasis on cycloaddition reactions of heterocyclic compounds both with and without supports, applications in supramolecular chemistry and the reproducibility and scalability of organic reactions involving the use of microwave irradiation techniques.

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Section: Diels-alder Reactions Of Furanssupporting

confidence: 72%

“…( 80 The differences observed between carbonyl and nitrile compounds were not easy to explain and it was necessary to carry out theoretical studies into the different reaction pathways [79].…”

Section: Diels-alder Reactions Of Furansmentioning

confidence: 99%

Microwave-Assisted Reactions in Heterocyclic Compounds with Applications in Medicinal and Supramolecular Chemistry

Hoz¹,

Díaz‐Ortiz²,

Moreno³

et al. 2007

CCHTS

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“…In this regard, the solid obtained by treating amorphous silica with Et 2 AlCl has proved to give an excellent heterogeneous catalyst for a variety of Diels−Alder reactions. − Notably, this catalyst can be stored in the open air and it is recoverable, keeping a large part of its catalytic activity, a fact that is unusual in aluminum-derived Lewis acids. Furthermore, it has been shown that this catalyst can be efficiently used to promote some Diels−Alder reactions that either do not take place in the presence of conventional Lewis acids or take place with poor selectivities. − …”

Section: Introductionmentioning

confidence: 99%

On the Nature of the Lewis Acid Sites of Aluminum-Modified Silica. A Theoretical and Experimental Study

et al. 1999

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The structures and relative Lewis acidities of the catalytic sites of four aluminum-modified silicas have been studied by means of theoretical calculations on model compounds, as well as by spectroscopic and catalytic experiments. Theoretical calculations indicate that the silica treated with Et2AlCl has aluminum sites that are more acidic than those of AlCl3. The thermic treatment of the aluminum-modified silicas leads to the appearance of new, very strong acidic sites, as shown by infrared and reactivity experiments. A possible structure for these sites is proposed on the basis of the theoretical calculations.

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“…[1][2][3][4][5][6] Zeolites are one of the best supports for catalysts in the petro-and organo-chemical industries. Zeolites ion-exchanged by transition metal ions are also useful catalysts.…”

Section: Introductionmentioning

confidence: 99%

“…2 ZnCl2, ZnI2, and TiCl4 supported on silica gel are more efficient catalysts in various organic reactions, [3][4][5] such as the Friedel-Crafts alkylation of benzene with alkyl chlorides 3 and Diels-Alder reactions with different dienophiles 4,5 even though ZnX2 and TiCl4 are already good catalysts for these reactions. 3 The applicability of these materials in Diels-Alder reactions of furan is improved by supporting it on silica gel.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Crystal Structure of Zinc Iodide in the Sodalite Cavities of Zeolite A (LTA)

2007

Bulletin of the Korean Chemical Society

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The crystal structure of ZnI2 molecule synthesized in zeolite A (LTA) has been studied by single-crystal X-ray diffraction techniques. A single crystal of |Zn6|[Si12Al12O48]-LTA, synthesized by the dynamic ion-exchange of |Na12|[Si12Al12O48]-LTA with aqueous 0.05 M Zn(NO3)2 and washed with deionized water, was placed in a stream of flowing 0.05 M KI in CH3OH at 294 K for four days. The resulting crystal structure of the product (|K6Zn3(KI)3(ZnI2)0.5|[Si12Al12O48]-LTA, a = 12.1690(10) Å) was determined at 294 K by single-crystal X-ray diffraction in the space group Pm m. It was refined with all measured reflections to the final error index R1 = 0.078 for 431 reflections which Fo > 4σ (Fo). At four crystallographically distinct positions, 3.5 Zn 2+ and nine K + ions per unit cell are found: three Zn 2+ and five K + ions lie on the 3-fold axes opposite 6-rings in the large cavity, two K + ions are off the plane of the 8-rings, two K + ions are recessed deeply off the plane of the 8-rings, and the remaining a half Zn 2+ ion lie on the 3-fold axes opposite 6-rings in the sodalite cavity. A half Zn 2+ ion and an I − ion per unit cell are found in the sodalite units, indicating the formation of a ZnI2 molecule in 50% of the sodalite cavities. Each ZnI2 (Zn-I = 3.35(5) Å) is held in place by the coordination of its one Zn 2+ ion to the zeolite framework oxygens and by the coordination of its two I − ions to K + ions through 6-rings (I-K = 3.33(8) Å). Three additional I − ions per unit cell are found opposite a 4-ring in the large cavity and form a K3I 2+ and two K2ZnI 3+ ionic clusters, respectively.

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Comparison of AlEt2Cl and ZnCl2 supported on silica gel as catalysts of Diels-Alder reactions. Influence of the nature of the dienophile

Cited by 11 publications

References 15 publications

Microwave-Assisted Reactions in Heterocyclic Compounds with Applications in Medicinal and Supramolecular Chemistry

Microwave-Assisted Reactions in Heterocyclic Compounds with Applications in Medicinal and Supramolecular Chemistry

On the Nature of the Lewis Acid Sites of Aluminum-Modified Silica. A Theoretical and Experimental Study

Synthesis and Crystal Structure of Zinc Iodide in the Sodalite Cavities of Zeolite A (LTA)

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