MCAT-53™: An Air Stable Arene Ruthenium Catalyst for C–C Cross-Coupling

Common Applications

MCAT-53™is a proprietary recyclable ruthenium-containing catalyst for C–C coupling reactions in aqueous media. In contrast to Pd-catalyzed C–H activated and directing group (DG) directed C–C coupling reactions, MCAT-53™ achieves C–H-activated C–C coupling in water under ligand-free conditions, requiring no auxiliary oxidants (such as Copper(II) salts and Silver(I) salts, or benzoquinone). The catalyst is tailor made to work in distilled / deionized water.

This first of its class, bench- and air-stable, MCAT-53™ will find wide utility in cost-effective and greener alternatives in manufacturing processes in the chemical enterprise. This catalyst that manifests its action in aqueous solutions has been developed by Chicago Discovery Solutions, USA.

Typical Reaction Scheme

The catalyst MCAT-53™ is added to the mixture of two aryl moieties (variously substituted) to get C–C coupling in water such as DG directed C–H activated C–C coupling.

 

MCAT-53™ reaction

Representative Example

General reaction of C-H arylation with MCAT-53TM  (ref 1, JACS, 2018):

To a reaction flask equipped with a stirring bar was added substrate (1.0 mmol) and 5.0 mL water (DI/distilled) followed by sequential addition of potassium carbonate (2.0 mmol) and aryl/heteroaryl halide (1.2 to 2.5 mmol). Immediately, MCAT-53TM ruthenium catalyst (40.0 mg, 0.07 mmol) was added to the slightly cloudy mixture. The orange brown solution was heated under reflux (turned black) and allowed to stir vigorously for 1 to 8 hrs. Stirring should be vigorous but not so vigorous so as to splatter reagents on the flask walls (around 600 ppm). The addition of MCAT-53TM was done at last during the reaction set up. A rapid reflux is maintained during the reaction. The heterogeneous reaction mixture was then diluted with a minimum volume of ethyl acetate (EA) (1 X 5 mL). The organic layer was separated, and washed with water (1 X 5 mL) and dried over anhydrous Na2SO4. The volatiles were removed under vacuum to afford the crude product. 1H NMR was used to determine the conversion and the ratio between mono- and di-arylated products. Subsequently, the crude mixture was purified by filtration over a small silica gel plug or flash chromatography using silica gel as required.  The structure of the unknown compounds was established by spectroscopic methods (data given below).  Spectroscopic data of the known compounds were verified with the literature for confirmation purpose.

We have observed effect associated with heating rate and the order of addition of various reagents. We recommend starting reflux of the reaction mixture soon after the addition of MCAT-53TM. We have carried out all the reactions in ambient atmosphere and with the reflux condenser efficiently cooled by water. Reflux condenser was left open to air. We also recommend consulting MSDS of reactants for safety under the conditions described before setting up the reactions under these conditions. The products either solidified upon cooling or were extracted with a small amount of ethyl acetate.

Materials

     

References

  1. Mehta A., Saha B.,Koohang, A. A., Chorghade M. Org. Process Res. Dev., 2018, 22, 9,1119-1130.

 

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