Imidazolinium and amidinium salts as Lewis acid organocatalysts

• Oksana Sereda,
• Nicole Clemens,
• Tatjana Heckel and
• René Wilhelm

Beilstein J. Org. Chem. 2012, 8, 1798–1803, doi:10.3762/bjoc.8.205

• –Alder reaction with ethyl crotonthioate (1) and cyclopentadiene (2). Diels–Alder reaction catalysed with imidazolinium salts. Ring opening of thiirane 12. Ring opening of epoxide 14. Synthesis of bis-imidazolium salt 17. Synthesis of amidinium salt 21. Diels–Alder reaction with 10 mol % catalyst

Extending the utility of [Pd(NHC)(cinnamyl)Cl] precatalysts: Direct arylation of heterocycles

• Anthony R. Martin,
• Anthony Chartoire,
• Alexandra M. Z. Slawin and
• Steven P. Nolan

Beilstein J. Org. Chem. 2012, 8, 1637–1643, doi:10.3762/bjoc.8.187

• preparation of the palladium complex 4. Following the strategy recently reported by Markó [23], we were successful in the synthesis of the IPr*Tol·HCl imidazolium salt 5 in a 53% overall yield (see Supporting Information File 1). Subsequently, 5 was treated with KOt-Bu in dry THF to generate the corresponding

Polysiloxane ionic liquids as good solvents for β-cyclodextrin-polydimethylsiloxane polyrotaxane structures

• Narcisa Marangoci,
• Rodinel Ardeleanu,
• Laura Ursu,
• Constanta Ibanescu,
• Maricel Danu,
• Mariana Pinteala and
• Bogdan C. Simionescu

Beilstein J. Org. Chem. 2012, 8, 1610–1618, doi:10.3762/bjoc.8.184

• Polymers, “Gheorghe Asachi” Technical University of Iasi, 700050 Iasi, Romania 10.3762/bjoc.8.184 Abstract An ionic liquid based on polydimethylsiloxane with imidazolium salt brushes was synthesized as a good solvent for β-cyclodextrin-polydimethylsiloxane rotaxane. As expected the PDMS-Im/Br ionic liquid

• interactions. The structure is stable in the 20 to 80 °C domain as proved by the oscillatory and rotational rheological tests. Keywords: cyclodextrins; imidazolium salt; ionic liquid; polyrotaxanes; polysiloxanes; Introduction Ionic liquids (ILs) are environmentally friendly solvents with great potential for

• decreases when their glass-transition temperature (Tg) increases [23]. In this respect, we have synthesized ILs based on polydimethylsiloxane with imidazolium salt brushes (PDMS-Im/S) with low Tg values in order to avoid a macroscopic phase separation in a mixture of ILs and CD-polydimethylsiloxane

N-Heterocyclic carbene-catalyzed direct cross-aza-benzoin reaction: Efficient synthesis of α-amino-β-keto esters

• Takuya Uno,
• Yusuke Kobayashi and
• Yoshiji Takemoto

Beilstein J. Org. Chem. 2012, 8, 1499–1504, doi:10.3762/bjoc.8.169

• -coupling of 1a was obtained. Encouraged by this result, we then attempted the other precatalysts 3b–e depicted in Figure 2. Imidazolium salt 3b and simple triazolium salt 3c gave no coupled product 5a (Table 1, entries 2 and 3). Further screening revealed that bicyclic triazolium salt 3d could catalyze the

Hybrid super electron donors – preparation and reactivity

• Jean Garnier,
• Douglas W. Thomson,
• Shengze Zhou,
• Phillip I. Jolly,
• Leonard E. A. Berlouis and
• John A. Murphy

Beilstein J. Org. Chem. 2012, 8, 994–1002, doi:10.3762/bjoc.8.112

• adopted as targets for synthesis. Of these, 10 and 11 are imidazolylidenes derived from an imidazolium salt. Donors derived from imdazolium salts are highly reactive and unstable; CV studies in MeCN have shown [15] that two-electron reduction of 13, bearing a single trimethylene bridge, which was intended

• 46, featuring an imidazolium salt and a pyridinylidene may well be relatively disfavoured. The pyridinylidene carbene in 46 should be less stabilised than the imidazolylidene carbene in 45, since in the former case, the carbene is stabilised by only one neighbouring N atom. Keeping the inter-ring C–C

N-Heterocyclic carbene/Brønsted acid cooperative catalysis as a powerful tool in organic synthesis

• Rob De Vreese and
• Matthias D’hooghe

Beilstein J. Org. Chem. 2012, 8, 398–402, doi:10.3762/bjoc.8.43

• preparation and characterization of a metal carbene complex in 1964 through nucleophilic attack of phenyllithium at tungsten hexacarbonyl followed by O-alkylation [1], and Arduengo described the preparation of the first free and stable N-heterocyclic carbene 2 by deprotonation of the corresponding imidazolium

• salt 1 in 1991 (Scheme 1) [2]. Two years earlier, Bertrand had reported the synthesis of [bis(diisopropylamino)phosphino]trimethylsilylcarbene as the first isolated free carbene [3]. The isolation of stable NHCs and their successful applications as ligands for the preparation of various metal complexes

Amines as key building blocks in Pd-assisted multicomponent processes

• Didier Bouyssi,
• Nuno Monteiro and
• Geneviève Balme

Beilstein J. Org. Chem. 2011, 7, 1387–1406, doi:10.3762/bjoc.7.163

• Pd-catalyzed cross-coupling approach starting from 1-chloro-2-iodobenzenes, phenylacetylene and a variety of primary amines [28][29]. The sequential three-component reaction was performed with the aid of an N-heterocyclic carbene-palladium complex generated in situ, derived from imidazolium salt 50

1-(4-Alkyloxybenzyl)-3-methyl-1H-imidazol-3-ium organic backbone: A versatile smectogenic moiety

• William Dobbs,
• Laurent Douce and
• Benoît Heinrich

Beilstein J. Org. Chem. 2009, 5, No. 62, doi:10.3762/bjoc.5.62

• n > 10 The lithium, sodium or potassium salt of our desired anion was dissolved in water and added to an aqueous solution of a 1-(4-alkyloxybenzyl)-3-methyl-1H-imidazol-3-ium bromide. A precipitation of the desired imidazolium salt occurred immediately. The reaction was stirred for a couple of hours

• . After centrifugation, the solvent was removed and the crude product was washed twice with water. The product was finally obtained pure by crystallization on a mixture from dichloromethane and diethyl ether. 1H NMR spectrum (in CD2Cl2) of 110–610. TGA measurements of wet and water free 112 imidazolium

• salt. TGA measurements of the two entire series 110–610 and 114–614 (rate 10° C·min−1, in air). Transition temperatures of 114–614 as a function of the anion (Cr = crystal; SmA: smectic A phase; Iso: Isotropic Liquid; Dec: decomposition). (a) Illustration of a single homeotropic monodomain, which is

A convenient method for preparing rigid-core ionic liquid crystals

• Julien Fouchet,
• Laurent Douce,
• Benoît Heinrich,
• Richard Welter and
• Alain Louati

Beilstein J. Org. Chem. 2009, 5, No. 51, doi:10.3762/bjoc.5.51

• layer was separated off, washed with water and dried over calcium chloride. Crystallization with dichloromethane and diethyl ether gave the corresponding imidazolium salt. 1-[4-(Dodecyloxy)phenyl]-3-methyl-1H-imidazol-3-ium tetrafluoroborate (1b) Following the general procedure using 1a (0.797 g, 1.69

Expedient syntheses of the N-heterocyclic carbene precursor imidazolium salts IPr·HCl, IMes·HCl and IXy·HCl

• Lukas Hintermann

Beilstein J. Org. Chem. 2007, 3, No. 22, doi:10.1186/1860-5397-3-22

• acetate fulfilled these requirements and gave optimal results in all imidazolium salt syntheses (entries 6,8,14). In the course of scale-up, the reactant concentration was identified as another important parameter (entry 2 vs 3; entries 5,10). The final, recommended procedure for the synthesis of 1,3

• behind such differences of the reaction outcome? To our knowledge, the mechanism of the Arduengo imidazolium salt synthesis has not been discussed in the literature. We propose that alkylation of the DADs A by formaldehyde and HCl (or TMSCl) leads to an iminium salt B (Scheme 2); analogous alkylations

• . Elimination of the oxy group then generates the imidazolium salt E. The electrocyclic mechanism proposed here, though not backed up by experimental data, is plausible considering related precedence [18][19][20] and because it proceeds via a favorable electroneutral intermediate (C). Alternative ionic