Asymmetric Vinylogous Diels-Alder Reactions Catalyzed by a Chiral Phosphoric Acid
作者:Xu Tian、Nora Hofmann、Paolo Melchiorre
DOI:10.1002/anie.201310487
日期:2014.3.10
to extend the synthetic utility of the Diels–Alder reaction to include a vinylogous reactivity space is described. A commercially available chiralphosphoricacid catalyst effectively activates cyclic 2,4‐dienones towards a vinylogous [4+2] cycloaddition with 2‐vinylindoles, which leads to stereochemically dense tetrahydrocarbazoles. The reaction proceeds with a high level of remote stereocontrol and
Control of Remote Stereochemistry in the Synthesis of Spirocyclic Oxindoles: Vinylogous Organocascade Catalysis
作者:Xu Tian、Paolo Melchiorre
DOI:10.1002/anie.201301017
日期:2013.5.10
Remote control: The title reaction facilitates the synthesis of complex chiral molecules while selectively forging multiple stereocenters at distant positions, namely five and six bond lengths away from the catalyst chiral fragment (see scheme; Boc=tert‐butoxycarbonyl). The potential of the strategy is demonstrated through the one‐step preparation of spirocyclopentane oxindoles having four contiguous
Aminocatalytic Enantioselective 1,6 Additions of Alkyl Thiols to Cyclic Dienones: Vinylogous Iminium Ion Activation
作者:Xu Tian、Yankai Liu、Paolo Melchiorre
DOI:10.1002/anie.201202392
日期:2012.6.25
presence of chiral amines, 2,4‐dienones are activated toward the attack of a nucleophile at the δ position, a mode of activation that is termed vinylogous iminiumion catalysis. Specifically, the 1,6 addition of alkyl thiols to β‐substituted cyclic dienones was catalyzed by a cinchona‐based primary amine; the reaction was highly stereoselective and displayed high selectivity for reaction at the δ position
The enantioselective and diastereoselective control of 1,3-dipolarcycloadditionreactions to β-substituted cyclic enones has been developed. The 1,3-dipolarcycloaddition of phthalazinium dicyanomethanides with cyclic dienones affords chiral tetrahydropyrrolo[2,1-a]phthalazine derivatives 3 through vinylogous iminium ion activation by combining a cinchona-based primary amine C3 and a chiral camphorsulfonic
已经开发出对β-取代环烯酮的1,3-偶极环加成反应的对映选择性和非对映选择性控制。二氰基甲烷化物与环状二烯酮的 1,3-偶极环加成反应通过金鸡纳基伯胺C3和手性樟脑磺酸添加剂的插烯亚胺离子活化得到手性四氢吡咯并[2,1- a ]酞嗪衍生物3 。相反,使用较弱的 3,5-双(三氟甲基)苯甲酸添加剂,二氰基二氮杂萘鎓与 β-取代环烯酮的 1,3-偶极环加成反应生成手性六氢异吲哚并[1,2- a ]酞嗪-10(8 H )-一衍生物4通过内二烯胺活化具有出色的立体控制能力。
Alkene-Assisted Nickel-Catalyzed Regioselective 1,4-Addition of Organoboronic Acid to Dienones: A Direct Route to All-Carbon Quaternary Centers
A nickel-catalyzed highly regioselective 1,4-addition reaction of boronic acids to dienones to form products with an all-carbon quaternary center is described. The 3-alkenyl group of dienones is the key for the reaction to proceed smoothly. A mechanism involving the coordination of the dienyl group to the nickel center is proposed.