954-55-2Relevant academic research and scientific papers
Reaction of Lithiated Propargyl Ethers with Carbonyl Compounds-A Regioselective Route to Furan Derivatives
Linder, Igor,Klemme, Robby,Reissig, Hans-Ulrich
, p. 765 - 774 (2020/11/13)
The deprotonation of 3-Aryl-substituted alkyl propargyl ethers with n-butyllithium provides an ambident anion that reacts with carbonyl compounds to provide mixtures of γ-substituted products with alkoxyallene substructure and of α-substituted propargyl ethers. The ratio of the two product types strongly depends on the solvent: in diethyl ether the γ-substituted products predominate whereas the more polar tetrahydrofuran favors the α-Adducts. The primary addition products undergo 5-endo-trig or 5-endo-dig cyclizations under various reaction conditions to afford isomeric furan derivatives. The highest selectivity in favor of α-substituted products was achieved by employing a MOM-protected propargyl ether. During the protonation step no evidence for a proton shift leading to an isomeric allenyl anion was found. A brief mechanistic discussion tries to rationalize the observed regio? selectivities.
Sodium Chloride Catalyzed Regioselective Trifluoromethylthiolation of Furans
Ernst, Johannes B.,Rakers, Lena,Glorius, Frank
supporting information, p. 260 - 268 (2016/12/24)
Here, we report the catalytic trifluoromethylthiolation of furans employing sodium chloride as an inexpensive, abundant and ecologically friendly catalyst. The developed method exhibits perfect regioselectivity and a high functional group tolerance. Furth
Sustainable Micellar Gold Catalysis - Poly(2-oxazolines) as Versatile Amphiphiles
Lempke, Linda,Ernst, Andrea,Kahl, Fabian,Weberskirch, Ralf,Krause, Norbert
, p. 1491 - 1499 (2016/05/19)
The application of five polymer amphiphiles in the gold-catalyzed allene cycloisomerizations under aqueous micellar conditions is described. The polymers were prepared by ring-opening cationic polymerization based on poly(2-methyl-2-oxazoline) as hydrophilic segment and different hydrocarbon- or fluorocarbon-based hydrophobic segments. The catalytic activity in the gold-catalyzed allene cyclization is strongly dependent on the type of gold precursor, the salt concentration in the bulk aqueous medium, and the concentration of the polymeric amphiphile. Best results were obtained with 2 mol% of gold(III) bromide, 1 mM of amphiphile and 5 M sodium chloride, affording over 80% yield for different heterocyclic products. The catalyst system is also suitable for the dehydrative cyclization of acetylenic diols to furans. Moreover, successful catalyst recycling was demonstrated in three consecutive runs when using optimized extraction conditions.
Leveraging the micellar effect: Gold-catalyzed dehydrative cyclizations in water at room temperature
Minkler, Stefan R. K.,Isley, Nicholas A.,Lippincott, Daniel J.,Krause, Norbert,Lipshutz, Bruce H.
, p. 724 - 726 (2014/03/21)
The first examples of gold-catalyzed cyclizations of diols and triols to the corresponding hetero- or spirocycles in an aqueous medium are presented. These reactions take place within nanomicelles, where the hydrophobic effect is operating, thereby driving the dehydrations, notwithstanding the surrounding water. By the addition of simple salts such as sodium chloride, reaction times and catalyst loadings can be significantly decreased.
Cationic gold(I)-mediated intramolecular cyclization of 3-alkyne-1,2-diols and 1-amino-3-alkyn-2-ols: A practical route to furans and pyrroles
Egi, Masahiro,Azechi, Kenji,Akai, Shuji
supporting information; experimental part, p. 5002 - 5005 (2009/12/26)
The intramolecular cyclizations of the 3-alkyne-1,2-diols and the 1-amlno-3-alkyn-2-ols with a low catalyst loading (0.05-0.5 mol %) of (Ph 3P)AuCl - AgNTf2 or (Ph3P)AuCl-AgOTf proceeded at room temperature to provide a variety of substituted furans and pyrroles In excellent yields (85-98% yields). This method Is also fully applicable to the conversion of several dozen grams of the substrate using only 0.05 mol % each of the Au and Ag catalysts.
Unexpected intermolecular Pd-catalyzed cross-coupling reaction employing heteroaromatic carboxylic acids as coupling partners
Forgione, Pat,Brochu, Marie-Christine,St.-Onge, Miguel,Thesen, Kris H.,Bailey, Murray D.,Bilodeau, Francois
, p. 11350 - 11351 (2007/10/03)
Aryl-substituted five-membered heteroaromatics have attracted great interest over the past years due to their presence in a large number of pharmaceuticals and natural products. Recently, an advance in the preparation of these scaffolds was achieved by employing a C-H functionalization strategy. This method allows easy access to these biaryl motifs by precluding the necessity of preparing specific coupling partners, although poor regioselectivity is sometimes observed when more than one reactive C-H is present on the substrate. In an effort to circumvent this liability, we envisioned the use of a carboxylic acid moiety as a blocking group that could be later functionalized or removed. Remarkably, the coupling was found to occur exclusively at the position previously occupied by the acid, even in the presence of a reactive C-H group. This selective transformation was also found to proceed with other heteroaromatic carboxylic acids, allowing for the preparation of a variety of aryl-substituted heteroaromatics that would be difficult to obtain via other methods. Copyright
(Alkoxyallyl)sulfones as enal and enone β-anion equivalents. Synthesis of mono-, di- and trisubstituted furans
Craig, Donald,Etheridge, Christopher J.
, p. 15289 - 15310 (2007/10/03)
Treatment of variously-substituted (alkoxyallyl)sulfones 1, 7-9 with strong base followed by aldehydes gives alcohol adducts 5. These may be converted into a wide range of substituted furans 6 by exposure to acid, or to silica gel in dichloromethane containing sulfuric acid in some cases.
Stereoselective Cyclopropanation of 1-Azadienes with Fischer Carbene Complexes
Barluenga, Jose,Tomas, Miguel,Lopez-Pelegrin, Jose A.,Rubio, Eduardo
, p. 665 - 666 (2007/10/02)
1-Aza-1,3-dienes, including a 1-aza-1,3,5-triene, are cyclopropanated by pentacarbonyl(methoxy)phenylchromium to give trans-cyclopropaneimines stereoselectively; their transformation into cyclopropane aldehydes and five-membered heterocycles is also descr
