The Role of Amide Solvents in the Formation of Ethylene Glycol from Synthesis Gas

Unprecedented Catalytic Hydrogenation of Urea Derivatives to Amines and Methanol

“…In fact, alkyl urea compounds have been used as solvents in catalytic hydrogenation reactions. For example, rhodium‐catalyzed hydrogenation of carbon monoxide to ethylene glycol under very high pressure ( p (H 2 )=200 bar) and at elevated temperature (200 °C) using N , N , N ′, N ′‐tetramethylurea (TMU) as an inert solvent was reported 4. In addition, sugar‐urea‐salt melts were used as “green solvents” for Rh‐catalyzed hydrogenation reactions and found to be sustainable reaction media 5…”

“…Traces of the corresponding dialkyl formamides were also observed in these cases. Although moderate yields were obtained for the hydrogenation of tetra‐substituted urea, these compounds have been used as inert polar solvents for hydrogenation reaction under very high hydrogen pressure, without undergoing hydrogenation 4…”

Hydrogenation of Polar Bonds Catalysed by Ruthenium-Pincer Complexes

“…Notably, alkyl urea compounds have been used as solvents in catalytic hydrogenation reactions of other compounds and as 'green' solvents in metal-mediated organic transformations [90,91]. Unprecedented hydrogenation of urea derivatives was achieved with complex 6 as catalyst.…”

Unprecedented Catalytic Hydrogenation of Urea Derivatives to Amines and Methanol

“…Although moderate yields were obtained for the hydrogenation of tetrasubstituted urea, these compounds have been used as inert polar solvents for hydrogenation reaction under very high hydrogen pressure, without undergoing hydrogenation. [4] The observation of traces of formamides (Table 2, entries 5-6 and 10-11) suggests a stepwise hydrogenation reaction, in which a formamide along with one equivalent of amine is initially formed by the cleavage of a C À N bond, followed by fast hydrogenation of the formamide, which does not accumulate. [23] In support of faster hydrogenation of formamides as compared with the starting urea derivatives, heating a THF solution of complex 1 (0.02 mmol), bis(pentamethylene)urea and N-formylmorpholine (1 mmol each) at 110 8C for 12 h under H 2 (13.6 atm), resulted in almost complete conversion of N-formylmorpholine (to 89 % yield of morpholine and 93 % yield of methanol) and very low conversion (< 2 %) of bis(pentamethylene)urea (to piperidine and methanol; Scheme 2).…”

“…For example, rhodium-catalyzed hydrogenation of carbon monoxide to ethylene glycol under very high pressure (p(H 2 ) = 200 bar) and at elevated temperature (200 8C) using N,N,N',N'-tetramethylurea (TMU) as an inert solvent was reported. [4] In addition, sugar-urea-salt melts were used as "green solvents" for Rh-catalyzed hydrogenation reactions and found to be sustainable reaction media. [5] Notably, alkyl and aryl urea compounds are readily synthesized from reactions of amines with CO 2 in the presence of various catalysts, such as 1,8-diazabicyclo-[5.4.0]undec-7-ene, [6] CsOH, [7] Cs 2 CO 3 , [8] Au/polymers, [9] [Bmim]OH [10] or KOH/PEG1000, [11] and by using ionic liquids, N-methylpyrrolidone, and supercritical carbon dioxide as solvents.…”