A chiral Mn(III) complex supported by a covalent grafting method on modified graphene oxide was synthesized using 3-chloropropyltrimethoxysilane as a reactive surface modifier. The heterogeneous catalyst was characterized by X-ray diffraction, Fourier transform infrared spectra, thermogravimetric analysis, ultraviolet-visible spectra, nitrogen adsorption-desorption isotherms, transmission electron microscopy and atomic absorption spectroscopy. The catalytic potential of the heterogeneous catalyst and comparison with its homogeneous counterpart were studied for enantioselective epoxidation of various alkenes using m-chloroperbenzoic acid as an oxidant and it showed high selectivity and comparable catalytic reactivity with its homogeneous analogue. In addition, higher enantioselectivity and higher yield were observed in the presence of 4-methylmorpholine N-oxide and pyridine N-oxide, respectively. The catalyst was reused for several runs without significant loss of activity and selectivity.

A green and efficient method has been developed for Heck and Sonogashira reactions by a magnetic Co(iii) bi-functional catalyst.

No abstract

The regioselective ring-opening reactions of some epoxides with ammonium thiocyanate in the presence of a series of new phenol-containing macrocyclic diamides and also dibenzo-18-crown-6-, 18-crown-6-, benzo-15-crown-5-, and pyridine-containing macrocyclic diamide have been studied. The epoxides were subject to cleavage by NH(4)SCN in the presence of these catalysts under mild reaction conditions in various aprotic solvents. In this study, reagents and conditions have been discovered with which the individual beta-hydroxy thiocyanates can be synthesized in high yield and with more than 90% regioselectivity. The results can be discussed in terms of a four-step mechanism: (1) formation of complex between catalyst and NH(4)SCN, (2) release of SCN(-) nucleophile from the complex, (3) reaction of the active nucleophile at the less sterically hindered site in the epoxide, and (4) regeneration of catalyst. The major advantages of this method are as follows: (1) high regioselectivity, (2) simple regeneration of catalyst, (3) its reuse through several cycles without a decrease in activity, and (4) ease of workup of the reaction.