212782-77-9Relevant academic research and scientific papers
Trichloromethylative Olefin Cycloamination by Photoredox Catalysis
Harada, Shinji,Masuda, Ryuya,Morikawa, Takahiro,Nishida, Atsushi
, p. 4531 - 4535 (2021)
The trichloromethyl group is an important functionality. It is a useful synthetic moiety and appears in the structures of natural and biologically active compounds; hence, developing synthetic methods for its introduction into structural motifs is an important objective. Herein, we report an efficient chemistry for the trichloromethylations and cycloaminations of olefin. These reactions are realized in a single step and triggered by the addition of the trichloromethyl radical, generated from bromotrichloromethane by photoredox catalysis, to a double bond, with the resulting intermediate trapped through intramolecular reaction with an amino group. This process facilitates the construction of N-heterocycles having trichloromethyl units and tetrasubstituted carbons from simple compounds under mild conditions.
Construction of All-Carbon Quaternary Stereocenters by Scandium-Catalyzed Intramolecular C-H Alkylation of Imidazoles with 1,1-Disubstituted Alkenes
Lou, Shao-Jie,Mo, Zhenbo,Nishiura, Masayoshi,Hou, Zhaomin
supporting information, p. 1200 - 1205 (2020/02/04)
The exo-selective C-H cycloaddition of imidazoles to 1,1-disubstituted alkenes has been achieved for the first time by using half-sandwich scandium catalysts. A wide range of imidazole compounds bearing various 1,1-disubstituted aliphatic alkenes, styrenes, dienes, and enynes have been selectively converted in high yields to the corresponding bicyclic imidazole derivatives bearing β-all-carbon-substituted quaternary stereocenters. By using a chiral half-sandwich scandium catalyst, the asymmetric exo-selective cyclization has also been achieved with a high level of enantioselectivity.
Gold(I)-Catalyzed Enantioselective Annulations between Allenes and Alkene-Tethered Oxime Ethers: A Straight Entry to Highly Substituted Piperidines and aza-Bridged Medium-Sized Carbocycles
Marcote, David C.,Varela, Iván,Fernández-Casado, Jaime,Mascarenas, José L.,López, Fernando
supporting information, p. 16821 - 16833 (2018/12/11)
Piperidine scaffolds are present in a wide range of bioactive natural products and are therefore considered as highly valuable, privileged synthetic targets. In this manuscript, we describe a gold-catalyzed annulation strategy that allows a straightforward assembly of piperidines and piperidine-containing aza-bridged products from readily available alkene-tethered oxime ethers (or esters) and N-allenamides. Importantly, we demonstrate the advantages of using oxime derivatives over imines, something pertinent to the whole area of gold catalysis, and provide relevant mechanistic experiments that shed light into the factors affecting the annulation processes. Moreover, we also describe preliminary experiments demonstrating the viability of enantioselective versions of the above reactions.
Homohalocyclization: Electrophilic Bromine-Induced Cyclizations of Cyclopropanes
R?sner, Christian,Hennecke, Ulrich
supporting information, p. 3226 - 3229 (2015/07/15)
An efficient method for the halocyclization of cyclopropanes has been developed. The cyclopropanes undergo a 1,3-addition reaction to form homohalocyclization products compared to conventional alkene halocyclizations. The reaction can be induced by variou
Ligand-controlled regiodivergent nickel-catalyzed annulation of pyridones
Donets, Pavel A.,Cramer, Nicolai
supporting information, p. 633 - 637 (2015/03/04)
The 1,6-annulated 2-pyridone motif is found in many biologically active compounds and its close relation to the indolizidine and quinolizidine alkaloid core makes it an attractive building block. A nickel-catalyzed C-H functionalization of 2-pyridones and subsequent cyclization affords 1,6-annulated 2-pyridones by selective intramolecular olefin hydroarylation. The switch between the exo- and endocyclization modes is controlled by two complementary sets of ligands. Irrespective of the ring size, the regioselectivity during the cyclization is under full catalyst control. Simple cyclooctadiene promotes an exo-selective cyclization, whereas a bulky N-heterocyclic carbene ligand results in an endoselective mode. The method was further applied in the synthesis of the lupin alkaloid cytisine.
Enantioselective bromoaminocyclization using amino-thiocarbamate catalysts
Zhou, Ling,Chen, Jie,Tan, Chong Kiat,Yeung, Ying-Yeung
supporting information; experimental part, p. 9164 - 9167 (2011/08/04)
A facile and efficient enantioselective bromoaminocyclization of unsaturated sulfonamides has been developed using an amino-thiocarbamate catalyst. A range of enantioenriched pyrrolidines were prepared with up to 99% yield and 99% ee. The corresponding lactams could be obtained through oxidation of the pyrrolidines.
Chiral diselenides in asymmetric cyclization reactions
Fragale, Gianfranco,Wirth, Thomas
, p. 1361 - 1369 (2007/10/03)
The use of chiral selenium electrophile 6 generated in situ from the chiral diselenide 5 in asymmetric ring closure reactions of unsaturated alcohols, carboxylic acids and carbamates is presented herein. Tetrasubstituted carbon atoms can be generated selectively with diastereoselectivities up to 85% when geminal disubstituted alkenes are used. The cyclization of vinylic silanes leads to versatile building blocks for further synthetic transformations.
