32774-29-1Relevant articles and documents
Au(I)-Catalyzed Domino Cyclization of 1,6-Diynes Incorporated with Indole
Chen, Guzhou,Liu, Peng-Yu,Zou, Huanhuan,Hu, Jiadong,Fang, Xiaowu,Xu, Dongyang,He, Yu-Peng,Wei, Hongbo,Xie, Weiqing
supporting information, p. 2279 - 2284 (2021/04/05)
We disclose herein a Au(I)-catalyzed domino cyclization of 1,6-diynes incorporated with indole. This protocol enabled the diastereoselective buildup of indole-fused azabicyclo[3.3.1]nonanes from linear precursors. Density functional theory calculations showed that the reaction proceeded via an unprecedented cascade dearomatization/rearomatization/dearomatization process. Independent gradient model analysis revealed that a noncovalent attractive interaction between the distal alkyne and the Au/proximal complex was responsible for the chemoselectivity of the first spirocyclization step.
Improved and Flexible Synthetic Access to the Spiroindole Backbone of Cebranopadol
Christoffers, Jens,Schmidtmann, Marc,Wachtendorf, Daniel
supporting information, p. 6420 - 6423 (2020/09/02)
By changing the dimethylamino to a nitro group, a novel synthetic access to the spirocyclic opioid analgesic cebranopadol was developed that is much more efficient compared with the established route. On the basis of the α-acidity of α-nitrotoluene, the two-fold Michael addition to acrylate gave an acyclic precursor compound, which was easily transformed by Dieckmann condensation and decarboxylation to the cyclohexanone derivative needed for the annulation of the indole ring by an oxa-Pictet-Spengler reaction. As an additional benefit, the reduction of the nitro group furnished an amine, which could be late-stage-diversified to carboxamides, sulfonamides, ureas, and N-alkyl congeners. The transformation of the nitro group at the spirocyclic scaffold to the dimethylamino function of the actual title compound was achieved in one step with zinc/formic acid/formaldehyde in 83% yield.
A Cooperative Hydrogen Bond Donor–Br?nsted Acid System for the Enantioselective Synthesis of Tetrahydropyrans
Maskeri, Mark A.,O'Connor, Matthew J.,Jaworski, Ashley A.,Davies, Anna V.,Scheidt, Karl A.
supporting information, p. 17225 - 17229 (2018/12/05)
Carbocations stabilized by adjacent oxygen atoms are useful reactive intermediates involved in fundamental chemical transformations. These oxocarbenium ions typically lack sufficient electron density to engage established chiral Br?nsted or Lewis acid catalysts, presenting a major challenge to their widespread application in asymmetric catalysis. Leading methods for selectivity operate primarily through electrostatic pairing between the oxocarbenium ion and a chiral counterion. A general approach to new enantioselective transformations of oxocarbenium ions requires novel strategies that address the weak binding capabilities of these intermediates. We demonstrate herein a novel cooperative catalysis system for selective reactions with oxocarbenium ions. This new strategy has been applied to a highly selective and rapid oxa-Pictet–Spengler reaction and highlights a powerful combination of an achiral hydrogen bond donor with a chiral Br?nsted acid.