P-BEMP: A New Efficient and Commercially Available User-Friendly and Recyclable Heterogeneous Organocatalyst for the Michael Addition of 1,3-Dicarbonyl Compounds
Michaeladdition of 1,3-dicarbonyls with various Michael acceptors has been found to be catalyzed by commercially available, user-friendly and recyclable N-phenyl-tris(dimethylamino)iminophosphorane immobilized on polystyrene resin (P-BEMP). The reaction does not require anhydrous solvents or inert atmosphere and proceeds smoothly at room temperature leading to the corresponding adducts, which can
Ti-Catalyzed Straightforward Synthesis of Exocyclic Allenes
作者:Juan Muñoz-Bascón、Carmen Hernández-Cervantes、Natalia M. Padial、Míriam Álvarez-Corral、Antonio Rosales、Ignacio Rodríguez-García、J. Enrique Oltra
DOI:10.1002/chem.201304033
日期:2014.1.13
Exocyclicallenes constitute useful building blocks in organic synthesis and have recently been identified as key intermediates in the synthesis of natural products. Here the first general method for the most straightforwardsynthesis of exocyclicallenes reported to date is presented. This method is based on the Barbier‐type cyclization of propargyl halides catalyzed by titanium; a safe, abundant
Michael Reaction of Stabilized Carbon Nucleophiles Catalyzed by [RuH<sub>2</sub>(PPh<sub>3</sub>)<sub>4</sub>]
作者:Enrique Gómez-Bengoa、Juan M. Cuerva、Cristina Mateo、Antonio M. Echavarren
DOI:10.1021/ja961373w
日期:1996.1.1
also observed as side reactions. Catalysis by other ruthenium and rhodium complexes has been examined. Selectivity studies performed with malonate and disulfone donors indicate that the catalyst selectively activates Michael donors that can coordinate with ruthenium(II). Additionally, it has been shown that the reaction requires the presence of free phosphine. Therefore, the Michael reaction of stabilized
缺乏氰基的活性亚甲基化合物如丙二酸酯、β-酮酯、1,3-二酮、1,1-二砜、硝基化合物、Meldrum 酸和蒽酮与常见受体的迈克尔反应在乙腈溶液中在 [RuH2 (PPh3)4]作为催化剂。氰基乙酸盐在有机溶剂中比丙二酸盐酸性更强,也是该反应的极好底物。在许多情况下,也观察到由 [RuH2(PPh3)4] 催化的分子内羟醛反应作为副反应。已经研究了其他钌和铑配合物的催化作用。对丙二酸和二砜供体进行的选择性研究表明,该催化剂选择性地激活可以与钌 (II) 配位的迈克尔供体。此外,已经表明该反应需要存在游离膦。所以,稳定的烯醇化物的迈克尔反应似乎是钌和膦催化的反应。从实用的角度来看,使用随手准备...
reactions involving nickel‐catalyzed additions of (hetero)arylboronic acids to alkynes, followed by cyclization of the alkenylnickel intermediates onto tethered acyclic ketones to give chiral tertiary‐alcohol‐containing products in high enantioselectivities, are described. The reversible E/Z isomerization of the alkenylnickel intermediates enables overall anti‐arylmetallative cyclization to occur. The ring
Combined use of Tf2NH and In(OTf)3 effectively promotes the cyclization of alk-5-ynyl ketones to cyclopent-1-enyl ketones at 30 °C. Single use of Tf2NH or In(OTf)3 requires heating at 50 °C for efficient cyclization. The In(OTf)3-promoted reaction of certain alk-5-ynyl ketones gives cyclohept-2-enones mainly.