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81.
Methylenecyclopentanones were synthesized by the nickel-catalyzed [3+1+1] cycloaddition reactions of alkenyl Fischer carbene complexes with methylenecyclopropanes. The methylenecyclopropane was transformed into the C(2)-symmetric bis-cyclopentapyridazine derivative by reacting with p-toluenesulfonyl hydrazine. 相似文献
82.
Dr. Hugh Nakamura Manami Kawakami Dr. Chihiro Tsukano Prof. Dr. Yoshiji Takemoto 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(37):8701-8704
A concise route for construction of the ACDE ring skeleton in calyciphylline A type alkaloids was developed using an intramolecular [5+2] cycloaddition reaction of an oxidopyrylium species bearing a tetrasubstituted olefin. Key to the success of this reaction was the combination of acid and base, which accelerated the construction of this skeleton containing a spiro ring and vicinal quaternary carbon centers. The resultant tricyclic ADE ring compound was converted to an ACDE ring model through C−H oxidation and an aza-Wittig reaction. 相似文献
83.
Masato Saito Dr. Yusuke Kobayashi Prof. Dr. Yoshiji Takemoto 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(44):10314-10318
The reactions of thioamides with ortho-nitro-substituted iodonium ylides proceeded under mild conditions to give enaminones or thiazoles, depending on the iodonium ylide used. This protocol allowed the use of protic solvents, including aqueous solutions, and therefore coupling reactions with complex molecules such as peptides or steroids were possible. A mild and efficient method for the synthesis of various iodonium ylides was established. DFT calculations suggested that the halogen bonding between a thioamide and iodonium ylide was important in this chemoselective coupling reaction. The potential use of enaminones conjugated with pharmaceuticals as prodrugs was also demonstrated. 相似文献
84.
The π-complexation of an arene to a transition metal center delivers many useful reactivities to the arene moiety. Although synthetic methodologies that take advantage of such π-coordination have mostly been developed as stoichiometric processes, there have been considerable recent advances in the catalytic transformations of aromatic molecules through their activation in the form of transition metal η6-arene complexes. These advances include the π-coordination catalyzed transformations of aryl-heteroatom and side-chain CH and CC bonds and the palladium-catalyzed CH functionalization in pre-formed transition metal η6-arene complexes. This digest paper aims to provide a concise view of these recent advances in the area of transition metal η6-arene complexes. 相似文献
85.
Toward concise access to functionalized amides and lactams, palladium‐catalyzed amidations of alkynes and alkenes with formamide derivatives were developed. Cyanoformamides having an alkynyl group were found to undergo intermolecular cyanoamidation in the presence of palladium catalyst to afford α‐alkylidene lactams. Whereas, when cyanoformamides that possess a 1,1‐disubstituted alkenyl group were used as starting materials, α,α‐disubstituted lactams were obtained. The latter reaction was extended to enantioselective transformation by utilizing optically active phosphoramidites as ligand. Furthermore, chloroformamides having a 1,1,2‐trisubsituted alkenyl group were found to give α‐vinyl‐lactams in the presence of palladium catalyst, base and silver salt. Additionally, formal intermolecular hydroamidation of alkenes was performed through one‐pot hydroboration‐carbamoylation sequence. © 2008 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 8: 386–394; 2008: Published online in Wiley InterScience ( www.interscience.wiley.com ) DOI 10.1002/tcr.20159 相似文献
86.
Satoru Arimitsu 《Journal of fluorine chemistry》2008,129(10):1047-1051
The addition of silver salts had an effect on the catalyst activity in the Pd(0)-catalyzed cyclization-coupling tandem reaction, as well as in the Rh(I)-catalyzed Pauson-Khand reaction. The cationic palladium complex generated from Pd(PPh3)4 (2.5 mol%) with AgSbF6 (1.5 equiv.) activates the triple bond of 2,2-difluoropropargylic amides to give the 4,5-disubstituted 3,3-difluoro-γ-lactams, through a sequential 5-endo-dig cyclization and cross-coupling reaction. The γ-lactam was transformed into ring-opened monofluorovinylic compounds after silica-gel chromatography. Pauson-Khand reaction of fluorinated 1,7-enyne amides using catalytic amounts of [Rh(COD)2]2 (5 mol%) and AgOTf (20 mol%) gave the corresponding gem-difluorinated bicyclic lactam. 相似文献
87.
A concise synthesis of the CDE ring system of the tetrahydroisoquinoline antitumor alkaloids such as saframycins, renieramycins, and ecteinascidins has been developed. Both Au(I)-catalyzed intramolecular hydroamidation of alkynylamide and NBS-mediated oxidative Friedel-Crafts cyclization of the resulting 2-ketopiperazine were utilized as key reactions. 相似文献
88.
89.
A one-pot synthesis of C1-elongated amides starting from olefins and carbamoyl chlorides has been developed. Alkylboranes, generated by hydroboration of terminal olefins with 9-BBN-H, underwent smooth coupling with carbamoyl chlorides in the presence of palladium catalyst and Cs2CO3. 相似文献
90.
Kamikawa K Takemoto I Takemoto S Matsuzaka H 《The Journal of organic chemistry》2007,72(19):7406-7408
[5]- and [6]helicenes were synthesized in moderate to good yields from Z,Z-bis(bromostilbene)s by palladium-catalyzed double C-H arylation reaction. This method can be applied to the syntheses of helicenes possessing electron-deficient substituents. 相似文献