6719-02-4Relevant articles and documents
Development of effective bidentate diphosphine ligands of ruthenium catalysts toward practical hydrogenation of carboxylic acids
Saito, Susumu,Wen, Ke,Yoshioka, Shota
, p. 1510 - 1524 (2021/06/18)
Hydrogenation of carboxylic acids (CAs) to alcohols represents one of the most ideal reduction methods for utilizing abundant CAs as alternative carbon and energy sources. However, systematic studies on the effects of metal-to-ligand relationships on the catalytic activity of metal complex catalysts are scarce. We previously demonstrated a rational methodology for CA hydrogenation, in which CA-derived cationic metal carboxylate [(PP)M(OCOR)]+ (M = Ru and Re; P = one P coordination) served as the catalyst prototype for CA self-induced CA hydrogenation. Herein, we report systematic trial- and-error studies on how we could achieve higher catalytic activity by modifying the structure of bidentate diphosphine (PP) ligands of molecular Ru catalysts. Carbon chains connecting two P atoms as well as Ar groups substituted on the P atoms of PP ligands were intensively varied, and the induction of active Ru catalysts from precatalyst Ru(acac)3 was surveyed extensively. As a result, the activity and durability of the (PP)Ru catalyst substantially increased compared to those of other molecular Ru catalyst systems, including our original Ru catalysts. The results validate our approach for improving the catalyst performance, which would benefit further advancement of CA self-induced CA hydrogenation.
Cu(I)-Catalyzed Intramolecular Tandem Cyclization of N-Indole-Tethered Cyclopropenes: Synthesis of Functionalized Hydrogenated Diazabenzo[ a]cyclopenta[ cd]azulene Derivatives
Li, Peng-Hua,Yang, Song,Hao, Tong-Gang,Xu, Qin,Shi, Min
supporting information, (2019/05/07)
A Cu(I)-catalyzed [3 + 2] intramolecular cycloaddition reaction of N-indole-tethered cyclopropenes is presented in this paper. This reaction starts from the formation of ?-allyl cationic intermediate or its resonance-stabilized metal carbenoid intermediate upon activation of cyclopropene with Cu(I) catalyst and a Friedel-Crafts-type cyclization to give functionalized hydrogenated diazabenzo[a]cyclopenta[cd]azulenes in good to excellent yields along with moderate to good dr values. The asymmetric variant of this cycloaddition reaction can be realized, giving the desired products with moderate ee values.
Enantioselective Fujiwara-Moritani indole and pyrrole annulations catalyzed by chiral palladium(II)-NicOx complexes
Schiffner, Julia A.,Woeste, Thorsten H.,Oestreich, Martin
supporting information; experimental part, p. 174 - 182 (2010/04/02)
The catalytic asymmetric Fujiwara-Moritani ring closures of several indole-and pyrrole-based cyclization precursors are reported. These unprecedented oxidative palladium(II)-catalyzed annulations allow for the formation of a stereogenic quaternary carbon atom, and decent levels of enantiocontrol are seen in 5-exo-trig cyclizations (54% ee for an indole and 76% ee for a pyrrole) while 6-exo-trig ring closures afford essentially racemic material. Novel oxazoline ligands with a nicotine platform (NicOx) are pivotal for good catalytic turnover as conventional PyOx ligands failed to produce acceptable chemical yields. The preparation of these NicOx ligands as well as the syntheses of the cyclization precursors are described in detail.