Hydrogenation of dicarboxylic acids to diols using Ruthenium catalyst

Piero Frediani, Luca Rosi, Dario Vannucchi
 Department of Organic Chemistry - University of Florence, via della Lastruccia, 13 - 50019 Sesto Fiorentino (FI)

RuH₄(CO)₈(PBu₃)₄ catalyzes selectively the reduction of disubstituited dicarboxylic acids to esters but is not able to reduce the esters to the corresponding alcohols.

On these bases, recently 1, we have settled  a convenient procedure for the reduction of 1,4-dicarboxylic acid to isotopomeric g-butyrolactones containing 2, 4 or 6 deuterium atoms  using Ru₄H₄(CO)₈(PBu₃)₄ as homogeneus catalyst under a D₂ pressure.

Tetradeuterated gamma-butyrolactone-[3,4,5,5-D₄] from maleic or fumaric acids, dideuterated gamma-butyrolactone-[5,5-D₂] from succinic acid and hexadeuterated gamma-butyrolactone-[3,3,4,4,5,5-D₆] from acetylenedicarboxylic acid.

Now our interest is focused on the syntheses of differently deuterated 1,4-butandiols starting from the appropiate dicarboxylic acids. Aware of the ability of the [Ru(acac)₃]/MeC(CH₂PPh₂)₃ system to catalyze, in the homogeneous, the hydrogenation of dimetyl oxalate to ethylenglycol, we have explored to employ such system in the one-pot syntheses of 1,4-butanediol (1,4-BD) from gamma-butyrolactone (GBL) or fumaric acid . The catalyst tested gives up to 49.6 yiled of 1,4-BTD from fumaric acid using methanol as solvent.

Reaction conditions and preliminary results are collected in the table below:

 Substrate 1.77 mmol, Ligand/Ru 1.37, Ru(acac)₃ 0.021 mmol, Solvent 12 ml, p(H₂) 80 bar, Substrate/Zn 1/0.26. DMS: Dimethyl succinate, MHS: Methyl 4-hydroxysuccinate.

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