Sn(OTf)2 catalysed regioselective styrene oxide ring opening with aromatic amines

Porous Coordination Polymer MOF-808 as an Effective Catalyst to Enhance Sustainable Chemical Processes

The improvement of sustainable chemical processes plays a pivotal role in safe environmental and societal development, for example, by reducing the use of hazardous substances, preventing chemical waste, and improving the efficiency of chemical reactions to obtain added-value compounds. In this context, the porous coordination polymer MOF-808 (MOF, metal-organic framework) was prepared by a straightforward method in water, at room temperature, and was unequivocally characterized by powder X-ray diffraction, vibrational spectroscopy, thermogravimetric analysis, and scanning electron microscopy. MOF-808 material was applied for the first time as catalysts in ring-opening aminolysis reactions of epoxides. It demonstrated high activity and selectivity for reactions of styrene oxide and cyclohexene oxide with aniline, using a very low amount of an eco-sustainable solvent (0.5 mL of EtOH), at 70 °C. Moreover, MOF-808 demonstrated high stability in the catalytic reaction conditions applied, and a notable reuse capacity of up to 20 consecutive reaction cycles, without significant variation in its catalytic performance. In fact, this Zr-based porous coordination polymer prepared by environment-friendly conditions proved to be a novel efficient heterogeneous catalyst, promoting the ring-opening reaction of epoxides under more sustainable conditions, and using a very low amount of catalyst.

Bidentate Ligand Driven Intramolecularly Te…O Bonded Organotellurium Cations from Synthesis, Stability to Catalysis

A new series of unsymmetrical phenyl tellurides derived from 2-N-(quinolin-8-yl) benzamide ligand has been synthesized in a practical manner by the copper-catalyzed method by using diaryl ditelluride and Mg as a reductant at room temperature. In order to augment the Lewis acidity of these newly formed unsymmetrical monotellurides, these have been transformed into corresponding unsymmetrical 2-N-(quinolin-8-yl)benzamide tellurium cations. Subsequently, these Lewis acidic tellurium cations were used as chalcogen bonding catalysts, enabling the synthesis of various substituted 1,2-dihydroquinolines by activating ketones with anilines under mild conditions. Moreover, the synthesized 2-N-(quinolin-8-yl)benzamide phenyl tellurium cation has also catalyzed the formation of β-amino alcohols in high regioselectivity by effectively activating epoxides at room temperature. Mechanistic insight by 1 H and 19 F NMR study, electrostatic surface potential (ESP map), control reaction in which tellurium cation reacted explosively with epoxide, suggested that the enhanced Lewis acidity of tellurium center seems responsible for efficient catalytic activities under mild conditions enabling β-amino alcohols with excellent regioselectivity and 1,2-dihydroquinolines with trifluoromethyl, nitro, and pyridylsubstitution, which were difficult to access.

Metal triflate promoted synthesis of naphthalenes

A synthetic route to derive the skeleton of naphthalenes starting with isovanillin is described with modest total yields via the key transformation of metal triflate-mediated intramolecular benzannulation of o-formyl or o-benzoyl allylbenzenes in MeNO₂ at rt.

Heterometallic coordination polymers: syntheses, structures and heterogeneous catalytic applications

Heterometallic coordination polymers function as heterogeneous catalysts for various organic transformation reactions via preferential interaction with the substrates.

Mononuclear complexes of amide-based ligands containing appended functional groups: role of secondary coordination spheres on catalysis

Coordination complexes of amide-based ligands with appended heterocyclic rings create a hydrogen bonding cavity that effectively binds the substrate(s). Such cavity-based complexes function as reusable and heterogeneous catalysts for various organic transformations.

Electronic and chelation effects on the unusual C2-methylation of N-(para-substituted)phenylaziridines with lithium organocuprates

Density functional theory calculations with the B3LYP functional were performed for the title ring-opening reaction to understand the intrinsic activating and directing effects of the N-substituents, as well as the electron donating effect of the para-substituted (Y = Cl, H, Me) phenyl group at the more hindered benzylic C2 atom. The N-tosyl group (i.e., N-Tos) or the N-(2-pyridyl)sulfonyl group (i.e., N-Py) was introduced to activate the ring nitrogen atom (N1) and the para-substituted (Y = Cl, H, Me) phenyl group for the activation of the C2 atom. Conformational searches and geometry optimizations were performed for the N-(para-substituted)phenylaziridines (1∼6). Calculations indicate that the aziridine 6 (i.e., Py/Me) has the most elongated C2-N1 bond intrinsically due to the electronic activating effects, implying the aziridine 6 to be the most potent candidate for the more-hindered C2 opening. Transition states (TSs) were investigated for the prospective ring-opening paths (I∼IV), considering the types of intermolecular push-pull interactions between the N-activated phenylaziridines and the cuprate. The N-Py group provides an unique C2-favored TS along the path IV, which the N-Tos group cannot afford, due to the less charge transfer from the nucleophilic CH 3δ- of the cuprate into the electrophilic C2 atom. Furthermore, the e-donating effect of the para-substituents (Y = Cl, H, Me) enhances the C2 opening for the path IV. This study enables us to understand the unusual ring-opening phenomena in terms of electronic and directing effects and hence may serve as a tool to design substrates for highly regioselective ring openings.

Ruthenium-catalyzed selective monoamination of vicinal diols

The monoamination of vicinal diols in the presence of in situ generated ruthenium catalysts has been investigated. Among the various phosphines tested in combination with [Ru(3)(CO)(12)], N-phenyl-2-(dicyclohexyl-phosphanyl)pyrrole showed the best performance. After optimization of the reaction conditions this system was applied to different secondary amines and anilines as well as a number of vicinal diols. With the exception of ethylene glycol, monoamination of the vicinal diols occurred selectively and the corresponding amino alcohols were obtained in good yields, producing water as the only side product.