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Catalyzed Cyclization (catalyzed + cyclization)
Selected AbstractsNeutral Group-IV Metal Catalysts for the Intramolecular Hydroamination of AlkenesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 16 2008Carsten Müller Abstract A detailed comparison of the group-IV metal catalysts Ti(NMe2)4, Ind2TiMe2, Ind2ZrMe2 and Ind2HfMe2 in the intramolecular hydroamination of amino alkenes is presented. Among these catalysts, the benchmark catalyst Ti(NMe2)4 is the most active in the formation of pyrrolidines. A comparison between Ind2TiMe2, Ind2ZrMe2 and Ind2HfMe2 suggests that in the synthesis of pyrrolidines, Zr complexes show the highest catalytic activity of the group-IV metal catalysts. Although Ind2TiMe2 - and the Ind2ZrMe2 -catalyzed formation of a pyrrolidine is first-order in the concentration of the substrate, the corresponding Ti(NMe2)4 -catalyzed cyclization is second-order in the concentration of the substrate. The results obtained for the formation of piperidines catalyzed by Ti(NMe2)4, Ind2TiMe2, Ind2ZrMe2 and Ind2HfMe2 suggest that for these reactions, Ti catalysts show increased catalytic activity compared with the corresponding Zr catalysts. Unfortunately, the formation of aminocyclopentane side-products by C,H activation processes is a severe drawback of the Ti catalysts. The corresponding side-products are not formed in Ind2ZrMe2 - and Ind2HfMe2 -catalyzed reactions. However, the former catalyst gives better yields of the desired piperidine products. In contrast to the results obtained for the synthesis of pyrrolidines, the formation of a piperidine is zero-order in the concentration of the substrate for the indenyl catalysts Ind2TiMe2 and Ind2ZrMe2, and first-order for the homoleptic catalyst Ti(NMe2)4. Interestingly, Ind2TiMe2 is able to catalyze a slow hydroamination of an N -methylated amino alkene, whereas the homoleptic complex Ti(NMe2)4 as well as Ind2ZrMe2 and Ind2HfMe2 do not catalyze the same reaction. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] A Practical Gold-Catalyzed Route to 4-Substituted Oxazolidin-2-ones from N -Boc PropargylaminesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 21 2007Eun-Sun Lee Abstract AuI -catalyzed cyclization of N -Boc propargylamines into 4-alkylidene oxazolidin-2-ones is described. This modularapproach provides access to a variety of nonproteogenic 4-substituted oxazolidinones that are important in asymmetric synthesis and biological applications. The current flexible route is characterized by low catalyst loading, mild conditions, and operational simplicity.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Palladium-Catalyzed Formation of Cyclic Ethers , Regio-, Stereo- and Enantioselectivity of the ReactionEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 14 2007Anna Zawisza Abstract An efficient and stereoselective synthesis of 3-alkyl-3-hydroxymethyl-5-vinyltetrahydrofurans is described by the Pd0 -catalyzed cyclization of the methyl carbonates of ,,,-bis(hydroxymethyl)-,,,-unsaturated alcohols. The use of chiral ligands gave the corresponding THF derivatives in low to moderate enantiomeric ratios. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Sulfur-Assisted and 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU)-Catalyzed Cyclization of 2-Alkynylanilines for the Metal-Free Synthesis of Indole DerivativesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 13 2010Hongwei Zhou Abstract A sulfur-assisted and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)-catalyzed cyclization of 2-alkynylanilines for the metal-free synthesis of indole derivatives is reported. As a result of the metal-free process, the ready availability of the starting materials and the simple and convenient operation, the type of reaction presented here has potential utility in organic synthesis. A 10-gram scale preparation may demonstrate the possibility of its application in the environmentally friendly synthesis of indole derivatives. [source] | ||||||||||