Strem, part of Ascensus, is pleased to announce the introduction of a new catalyst capable of selective C-H oxidation.
White-Gormisky-Zhao Catalyst
(R,R) 25-4175, (S,S) 25-4160
Prof. M. Christina White and her group at University of Illinois Urbana-Champaign have excelled at discovering catalysts for selective C-H activation on molecules with a variety of different C-H bonds. Tertiary C-H bonds are energetically the easiest to activate compared to secondary C-H bonds, meaning that if both were able to access the catalyst active site, the tertiary C-H bond would be preferentially oxidized. This was indeed the case with their first generation of C-H oxidation catalysts, which could take hydrogen peroxide (H2O2) and perform selective oxidation of tertiary C-H bonds. These first generation catalysts are available in our catalog (26-0060, 26-0061). [1]
By changing the metal atom from Fe to Mn and enlarging the ligand around the metal atom in their new White-Gormisky-Zhao catalyst, tertiary C-H bonds cannot access the catalyst’s active site and were therefore left untouched while secondary C-H bonds, often on alkyl chains or on outer edges of target molecules, were selectively oxidized. By varying the amount of H2O2 in the reaction, they were able to oxidize the target carbon once (with 2 eq. of H2O2), to install a hydroxyl group, or twice (with 10 eq. of H2O2), to form a ketone. [2]
Building on this methodology, the White group recently published the ability of the White-Gormisky-Zhao catalyst to easily modify drug precursors, natural products, and antibiotics by installing a methyl group on the carbon adjacent to a heteroatom (usually N or O). This is a desirable modification that has a name, the “magic methyl effect,” which describes the tendency for this minor change in a molecule to drastically increase the potency of biologically active molecules. The White-Gormisky-Zhao catalyst carries out the first step in this two-step modification by first activating a C-H bond and introducing a hydroxyl group in the manner described above. In the second step, after using a Lewis acid to remove the hydroxyl group, the addition of trimethylaluminum installed the methyl group on the target molecule. [3]
The White group continues to find new uses for this catalyst, so stay on the lookout for new publications. These catalysts will play a significant role in the future of pharmaceutical research, and they are available in the Strem Catalog for R&D purposes. They come in two enantiomers, the R,R (25-4175) and S,S (25-4160), allowing for more selectivity in their performance. While 25-4175 is the hexafluoroantimonate salt, which is ready to use as received, note that 25-4160 has coordinated chloride ions, which gives it superior shelf life, but will require activation with silver hexafluoroantimonate (93-4748) prior to use. Choose wisely or get both enantiomers!
References:
Featured Products
25-4175 Bis(acetonitrile)[2,2'-[[(2R,2'R)-[2,2'-bipyrrolidine]-1,1'-diyl-κN1,κN1']bis(methylene)]bis[5-[2,6-bis(trifluoromethyl)phenyl]pyridine-κN]] Manganese(II) hexafluoroantimonate, Mn(R,R-CF3PDP): White-Gormisky-Zhao catalyst
25-4160 [2,2'-[[(1R,1'R,2S,2'S)-[2,2'-Bipyrrolidine]-1,1'-diyl-κN1,κN1']bis(methylene)]bis[5-[2,6-bis(trifluoromethyl)phenyl]pyridine-κN]] Manganese dichloride, Mn(S,S-CF3PDP) dichloride: White-Gormisky-Zhao catalyst precursor (2270959-23-2)
Related Materials
Catalysts
Metal Catalysts for Organic Synthesis
Metal Oxidation Catalyst