Tag: 900-1000

Shen, Zengming; Dornan, Peter K.; Khan, Hasan A.; Woo, Tom K.; Dong, Vy M. published an article on January 28 ,2009. The article was titled 《Mechanistic insights into the rhodium-catalyzed intramolecular ketone hydroacylation》, and you may find the article in Journal of the American Chemical Society.SDS of cas: 256390-47-3 The information in the text is summarized as follows:

Rhodium diphosphine catalysts, [Rh(dppp)2]BF4 and [Rh((R)-DTBM-SEGPHOS)]BF4 [dppp = 1,3-bis(diphenylphosphino)propane, DTBM-SEGPHOS = (4R)-[4,4′-bi-1,3-benzodioxole]-5,5′-bis(diarylphosphine), aryl = 3,5-di-tert-butyl-4-methoxyphenyl] exhibit high catalytic activity, chemo- and enantioselectivity in intramol. ketone group hydroacylation of oxo-substituted salicylaldehyde ethers, 2-RCOCHR1OC6H4CHO (1a-o), yielding 3-R-2,3-dihydro-1,4-benzodioxepin-5-ones I (2a-o; R1 = H, R = Ph, 4-CF3C6H4, 4-MeO2CC6H4, 4-ClC6H4, 4-FC6H4, 4-MeC6H4, 4-MeOC6H4, 2-naphthyl, Bu, iPr, tBu, PhCH2, Me, 2-furyl, 2-thienyl; rac-2p, R1 = R = Me; rac-2q, R1 = R = Ph). The reaction catalyzed by [Rh((R)-DTBM-SEGPHOS)]BF4 afforded seven-membered lactones 2a-o in large enantiomeric excess. A combined exptl. and theor. study aimed to elucidate the mechanism and origin of selectivity in this C-H bond activation process, is presented. Evidence is presented for a mechanistic pathway involving three key steps: (1) rhodium(I) oxidative addition into the aldehyde C-H bond, (2) insertion of the ketone C:O double bond into the rhodium hydride, and (3) C-O bond-forming reductive elimination. Kinetic isotope effects and Hammett plots support that ketone insertion is the turnover-limiting step. Detailed kinetic experiments were performed using both dppp and (R)-DTBM-SEGPHOS as ligands. With dppp, the keto-aldehyde substrate assists in dissociating a dimeric precatalyst [Rh2(μ-η6:κP,κP’-dppp)2][BF4]2 (8) and binds an active monomeric form of the catalyst. With [Rh((R)-DTBM-SEGPHOS)]BF4, there is no induction period and both substrate and product inhibition are observed In addition, competitive decarbonylation produces a catalytically inactive rhodium carbonyl species that accumulates over the course of the reaction. Both mechanisms were modeled with a kinetics simulation program, and the models were consistent with the exptl. data. D. functional theory calculations were performed to understand more elusive details of this transformation. These simulations support that the ketone insertion step has the highest energy transition state and reveal an unexpected interaction between the carbonyl-oxygen lone pair and a Rh d-orbital in this transition state structure. Finally, a model based on the calculated transition-state geometry is proposed to rationalize the absolute sense of enantioinduction observed using (R)-DTBM-SEGPHOS as the chiral ligand. In the experimental materials used by the author, we found (R)-(6,6′-Dimethoxybiphenyl-2,2′-diyl)bis[bis(3,4,5-trimethoxyphenyl)phosphine](cas: 256390-47-3SDS of cas: 256390-47-3)

(R)-(6,6′-Dimethoxybiphenyl-2,2′-diyl)bis[bis(3,4,5-trimethoxyphenyl)phosphine](cas: 256390-47-3) belongs to chiral phosphine ligands. Nucleophilic phosphine catalysis often involves the formation of Lewis adducts, namely phosphonium (di)enolate zwitterions, as reaction intermediates. SDS of cas: 256390-47-3 These intermediates are formed through nucleophilic attack of the phosphine catalysts at electron-poor nuclei (normally carbon atoms) and then proceed through several steps to form new chemical bonds.

Referemce:
Phosphine ligand,
Chiral phosphines in nucleophilic organocatalysis

In 2015,Angewandte Chemie, International Edition included an article by Pritzius, Adrian B.; Breit, Bernhard. Product Details of 256390-47-3. The article was titled 《Asymmetric Rhodium-Catalyzed Addition of Thiols to Allenes: Synthesis of Branched Allylic Thioethers and Sulfones》. The information in the text is summarized as follows:

A highly regio- and enantioselective hydrothiolation of terminal allenes, a reaction which fulfills the criteria of atom economy, is reported. Applying two chiral rhodium catalyst systems, a wide variety of thiols and allenes could be coupled. Oxidation gave access to the corresponding allylic sulfones in essentially enantiomerically pure form. The reaction tolerates a variety of functional groups and labeling experiments gave first insights into the reaction mechanism of this new methodol. In the experiment, the researchers used many compounds, for example, (R)-(6,6′-Dimethoxybiphenyl-2,2′-diyl)bis[bis(3,4,5-trimethoxyphenyl)phosphine](cas: 256390-47-3Product Details of 256390-47-3)

(R)-(6,6′-Dimethoxybiphenyl-2,2′-diyl)bis[bis(3,4,5-trimethoxyphenyl)phosphine](cas: 256390-47-3) belongs to chiral phosphine ligands. Nucleophilic phosphine catalysis often involves the formation of Lewis adducts, namely phosphonium (di)enolate zwitterions, as reaction intermediates. Product Details of 256390-47-3 These intermediates are formed through nucleophilic attack of the phosphine catalysts at electron-poor nuclei (normally carbon atoms) and then proceed through several steps to form new chemical bonds.

Referemce:
Phosphine ligand,
Chiral phosphines in nucleophilic organocatalysis

Formula: C50H56O14P2On November 12, 2014 ,《Copper-Catalyzed Diastereo- and Enantioselective Desymmetrization of Cyclopropenes: Synthesis of Cyclopropylboronates》 appeared in Journal of the American Chemical Society. The author of the article were Parra, Alejandro; Amenos, Laura; Guisan-Ceinos, Manuel; Lopez, Aurora; Garcia Ruano, Jose Luis; Tortosa, Mariola. The article conveys some information:

A novel Cu-catalyzed diastereo- and enantioselective desymmetrization of cyclopropenes to afford nonracemic cyclopropylboronates is described. Trapping the cyclopropylcopper intermediate with electrophilic amines allows for the synthesis of cyclopropylaminoboronic esters and demonstrates the potential of the approach for the synthesis of functionalized cyclopropanes. After reading the article, we found that the author used (R)-(6,6′-Dimethoxybiphenyl-2,2′-diyl)bis[bis(3,4,5-trimethoxyphenyl)phosphine](cas: 256390-47-3Formula: C50H56O14P2)

(R)-(6,6′-Dimethoxybiphenyl-2,2′-diyl)bis[bis(3,4,5-trimethoxyphenyl)phosphine](cas: 256390-47-3) belongs to chiral phosphine ligands. Nucleophilic phosphine catalysis often involves the formation of Lewis adducts, namely phosphonium (di)enolate zwitterions, as reaction intermediates. Formula: C50H56O14P2 These intermediates are formed through nucleophilic attack of the phosphine catalysts at electron-poor nuclei (normally carbon atoms) and then proceed through several steps to form new chemical bonds.

Referemce:
Phosphine ligand,
Chiral phosphines in nucleophilic organocatalysis