Search

[Display omitted] • Well-defined cyclic carbamoyl-Mn(I) complexes are prepared with improved stability. • Carbamoyl-Mn(I) accelerates alkenes epoxidation via Mn(III)=O and Mn(II)-O species. • CO 2 cycloaddition of epoxides was promoted by acidic N–H proton in carbamoyl unit. There is no precedent for the usage of transition metal carbamoyl complexes (typical hydrogenase models) as pre-catalysts for oxidation or CO 2 utilization purposes. In this work, we describe that carbamoyl-Mn(I) complexes are capable of selectively catalyzing both epoxidation of olefins and epoxides with carbon dioxide to form cyclic carbonates. The dual-role catalytic system was well adapted to a wide range of aromatic olefins, and the desired cyclic carbonates were obtained in moderate to excellent yields. Mechanistic investigations indicated that active Mn(II)-oxo and Mn(III)-oxo species were involved in the oxidation process. [ABSTRACT FROM AUTHOR]

An efficient palladium-manganese system for the Markovnikov selective alkoxycarbonylation reaction of aromatic and aliphatic alkenes was developed. [Display omitted] • A general and efficient palladium-manganese system for the Markovnikov selective alkoxycarbonylation reaction of alkenes. • By using the carbazole-derived phosphine ligand containing bipyridine moiety, various aromatic and aliphatic olefins were transformed into the corresponding esters in good yields with moderate to high branched selectivity. • Preliminary mechanistic studies reveal the respective contribution of palladium and manganese centers to achieve highly branch-selective alkoxycarbonylations. Carbazole derived phosphine ligands containing pyridine moiety were designed and prepared. It allows the challenging Pd-catalyzed Markovnikov-selective alkoxycarbonylation of aliphatic alkenes to give the branched ester products (28 examples; 51–97% branch selectivity). Preliminary mechanistic studies support that the bridging bromide between Pd and Mn centers is crucial for the enhancement of regioselectivity. [ABSTRACT FROM AUTHOR]

[Display omitted] • The first efficient ligand free iron-catalyzed hydroaminocarbonylation of alkynes to produce succinimides with NH 4 HCO 3 as the ammonia source. • With NH 4 HCO 3 as easy-to-handle ammonia source, a variety of internal and terminal alkynes were well tolerated in this catalytic system. • Preliminary mechanistic studies reveal the activation model involving interactions of NH 4 HCO 3 with both iron catalyst and alkyne substrates. Succinimide derivatives are valuable compounds in synthesis of natural products and pharmaceuticals. A catalytic hydroaminocarbonylation reaction was developed for the synthesis of succinimides from alkynes, CO and NH 4 HCO 3. The novel transformation proceeds in the presence of Fe 3 (CO) 12 without the need for expensive ligands or additives. Various substituted alkynes are selectively transformed into corresponding succinimides in good yields. Preliminary mechanistic studies suggest that NH 4 HCO 3 plays an important role in the formation and stabilization of iron catalyst. [ABSTRACT FROM AUTHOR]

A novel approach involving molybdenum disulfide (MoS 2) promoted in-situ generation of cobalt catalyst for alkoxycarbonylation reaction was presented. Cobalt(II) salts were transformed to highly active cobalt carbonyl species without using external reducing agents or applying harsh reaction conditions. Mechanism studies revealed that the defect-rich MoS 2 played the key role to abstract electron from CO and to reduce Co2+. [Display omitted] • S-defect MoS 2 promoted cobalt(II) reduction to cobalt(0) with CO as reductant under mild conditions. • Inexpensive and stable cobalt acetate as catalyst precursor instead of Co 2 (CO) 8. • MoS 2 with sulfur defects serves dual roles to abstract electron from CO and to reduce Co2+. • This work provides strategies for in-situ generation of low-valence metallic species. Herein, we presented a novel approach involving molybdenum disulfide (MoS 2) promoted in-situ generation of active cobalt catalyst for alkoxycarbonylation reaction, an industrial process for ester production. In this scenario, inexpensive cobalt(II) salts were transformed to highly active cobalt carbonyl species without using external reducing reagents or applying harsh reaction conditions. In-situ formed cobalt catalyst enabled high activity comparable to that using Co 2 (CO) 8 as catalyst. The generation of [Co(CO) 4 ]- anion under mild conditions was confirmed by both in-situ Fourier transformed infrared spectroscopy (FT-IR) and electrospray ionization mass spectrometry (ESI-MS). The detailed mechanism of this transformation revealed by X-ray photoelectron spectroscopy (XPS) and electrochemical analysis involved that carbon monoxide (CO) served dual roles as reductant and carbonyl ligand while the electron transfer to Co2+ cation took place over the MoS 2 surface with sulfur defects. [ABSTRACT FROM AUTHOR]

Reductive Strecker reaction of formamides to afford amino-acetonitriles was achieved via FeI 2 -catalysis. [Display omitted] • A new method to access amino acetonitriles using FeI 2 catalyst. • Better yields obtained than the use of Ir- or Rh-catalysts. • One pot synthesis of 13C-labelled amino acetonitriles from 13C-CO 2. • Successful application toward modular synthesis of acids, amines, heterocycles, etc. Strecker reaction is widely applied for the synthesis of amino acids from aldehydes, amines and cyanides. Herein, we report the FeI 2 -catalyzed reductive Strecker type reaction of formamides instead of aldehydes to produce amino acetonitriles. The challenging capture of carbinolamine intermediates by CN− was achieved via Fe catalysis. This approach afforded better yields than the use of Ir- or Rh-catalysts. The application ability of this methodology is demonstrated by 1) one-pot construction of (13C labeled) complex molecules from CO 2 via amino acetonitrile intermediates and 2) convenient production of homologated carboxylic acids from aldehydes. [ABSTRACT FROM AUTHOR]

Catalytic carbonylations of alkynes represent straightforward and atom-economic synthesis of α,β-unsaturated carbonyl compounds. One of the issues associated with the currently known catalytic systems is insufficient efficiency. In this context, Pd/ligand-catalyzed regioselective and efficient alkoxycarbonylation of terminal alkynes is desirable for the synthesis of α,β-unsaturated esters. Herein, we present the use of a newly designed bifunctional ligand for efficient Pd-catalyzed alkoxycarbonylation of alkynes. Both aliphatic and aromatic alkynes were smoothly transformed to the branched desired products with high selectivity (28 examples, 45–96% yields, 95.0–99.9% selectivity). [ABSTRACT FROM AUTHOR]