Strem Chemicals in collaboration with Takasago markets Ru-MACHO® —a ruthenium (II) PNP type pincer catalyst— (44-0071). Ru-MACHO® is a robust catalyst for a wide range of chemical transformations, such as homogenous hydrogenation of esters, methylation of primary amines, and dehydrogenation of secondary alcohols. Upon reduction with NaBH4, Ru-MACHO® produces Ru-MACHO®-BH (44-0074) which can be utilized for hydrogenation of esters under base free conditions.
Hydrogenation of Esters. The catalyst introduced by Kuriyama et. al. at Takasago is synthesized using [RuHCl(CO)-(PPh3)3] and HN(CH2CH2PPh2)2. It was named Ru-MACHO® because of the similarity of the structure of the ligand to a brawny athlete holding the ruthenium in place1. Ru-MACHO® is useful for hydrogenation of esters with high selectivity and diversity towards different substrates, and shows promising results for hydrogenation of esters containing chiral centers1.
44-0071 is also useful for hydrogenation of cyclic carbonates to produce diols and methanol2, fluorinated esters to produce fluorinated alcohols3, and diethyl oxalate4.
Dehydrogenation of alcohols. Different research groups have investigated the capability of this catalyst towards dehydrogenation of alcohols. Beller’s group, for instance, showed a catalytic amount of 44-0071 is able to convert isopropanol to acetone with a turnover frequency (TOF) of 1231 h-1 5. They further exploited the dehydrogenation ability of 44-0071 for the synthesis of alkyl esters from alcohols (e.g., ethyl acetate from ethanol)6 and producing hydrogen from methanol7, 8 and/or glycerol9.
Dehydrogenation of methanol in the presence of 44-0071 inspired other groups to use it for N-methylation of aromatic amines. Using aromatic amines and methanol Ogata et. al. prepared monomethylated secondary amines in high yields at 150 °C with low catalyst loading10.
Synthesis of amides. The Dong group reported using 44-0071 for the synthesis of amides and imines from alcohols and amines. They suggested the reaction occurs through an acceptor less dehydrogenation pathway.11 Later, Ru-MACHO® was utilized as a catalyst in the synthesis of formamides through N-formylation of various primary and secondary amines with H2 and CO2 12.
44-0071: Carbonylchlorohydrido[bis(2-(diphenylphosphinoethyl)amino]ruthenium(II), min.98% Ru-MACHO® (1295649-40-9)
44-0074: Carbonylhydrido(tetrahydroborato)[bis(2-diphenylphosphinoethyl)amino]ruthenium(II), min.98% Ru-MACHO®-BH (1295649-41-0)
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