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Cyclopentane Construction by Rh-Catalyzed Intramolecular C-H Insertion
Published in Dale W. Blackburn, Catalysis of Organic Reactions, 2020
Douglass F. Taber, Michael J. Hennessy, R. Scott Hoerrne, Krishna Raman, Robert E. Ruckle, Jonathan S. Schuchardt
It is apparent (entries 4-7) that steric factors also play an important role in governing selectivity. The ligands on the rhodium also influence selectivity. For entry 6, rhodium acetate gave a 3:1 ratio of cis25 to trans.26 With rhodium octanoate the ratio was 5:1, whereas with tetraphenylporphyrin rhodium chloride it was 15:1.
Carbon nanotube-zeolite composite catalyst - characterization and application
Published in Journal of Dispersion Science and Technology, 2021
Ádám Prekob, Viktória Hajdu, Béla Fiser, Ferenc Kristály, Béla Viskolcz, László Vanyorek
The core of the composite structure was zeolite (diam. 2 mm, 5 A molecule sieve, Roth). Nitrogen-doped bamboo-like carbon nanotubes (N-BCNTs) were synthetized on the zeolite beads to achieve the SoS system. During the CCVD synthesis of N-BCNTs n-butylamine (Scharlau Chem., reagent grade) was used as carbon source and nickel(II) nitrate hexahydrate (Ni(NO3)2·6 H2O, Merck Chem., purity 99,9999) as catalyst. The SoS system was decorated with three different catalytically active metals, Pd (reduced from palladium(II) chloride, PdCl2, Chinoin Ltd., 99%), Rh (reduced from rhodium-acetate dimer, [(CH3CO2)2Rh]2, Sigma-Aldrich, purity 99,99), and Pt (reduced from hexachloroplatinic acid hexahydrate, H2PtCl6·6H2O, Sigma-Aldrich, ACS reagent, ≥37.50% Pt basis). For the solvation of the PdCl2, Patosolv (alcohol mixture, Molar Chem.) was used. The activity of the three final catalysts (Pd-, Rh-, and Pt-SoS) was compared in 1-butene (Messer) hydrogenation (hydrogen, purity 4.0, Messer; nitrogen, purity 4.0, Messer).
Rhodium catalysis in the synthesis of fused five-membered N-heterocycles
Published in Inorganic and Nano-Metal Chemistry, 2020
Navjeet Kaur, Neha Ahlawat, Yamini Verma, Pranshu Bhardwaj, Pooja Grewal, Nirmala Kumari Jangid
A reactive 1,3-dipole thiocarbonyl ylide (218) was produced when thiocarbonyl group interacted readily with a metal carbene complex. The ability of thiocarbonyl compounds to decompose the diazo substrate was inhibited upon its coordination to a transition metal catalyst. The rhodium(II) carbene complexes were constructed from rhodium(II) carboxylate catalysts in the presence of thiocarbonyl compounds. The reaction needed high temperatures (in refluxing toluene or benzene). A metal carbene complex underwent intramolecular ring closure and 1,3-dipole cycloaddition to produce thiocarbonyl ylide (218). For thiocarbonyl ylides (218) a feasible reaction was ring closure to an episulfide (219). An olefin was obtained as final product (222) in most cases where sulfur was extruded further under the reaction conditions. Danishefsky et al.[159] utilized this cascade transformation for the total synthesis of (-)-indolizomycin (Scheme 50). In Danishefsky’s method, thiocarbonyl ylide (218) was produced when diazo ketone (217) was treated with rhodium acetate, subsequently thiocarbonyl ylide (218) was cyclized to episulfide (219) which isomerized to generate mercaptan (220). Mercaptan (220) was desulfurized by partially deactivated W-2 Raney nickel.[3b]
Copper-assisted synthesis of five-membered O-heterocycles
Published in Inorganic and Nano-Metal Chemistry, 2020
Navjeet Kaur, Yamini Verma, Neha Ahlawat, Pooja Grewal, Pranshu Bhardwaj, Nirmala Kumari Jangid
Doyle et al.[85] reported that formation of macrocyclic oxonium ylide and subsequent [2, 3]-sigmatropic rearrangement is also possible besides the synthesis of five- and six-membered oxonium ylides. The [2, 3]-sigmatropic rearrangement product was synthesized in major amounts together with intramolecular cyclopropanation product when propargyl-linked diazoacetate was reacted in the presence of Cu(MeCN)4PF6.[86,87] Intramolecular cyclopropanation occurred predominantly along with minor intramolecular carbon–hydrogen insertion when diazoacetate was reacted with rhodium acetate. Rhodium acetate catalysis afforded no trace of cyclic ylide formation/[2, 3]-sigmatropic rearrangement product. These results have shown that catalyst effected the competition between other metal carbene reaction pathways and intramolecular ylide formation (Scheme 23).[1b]