This study presents a first
report on ruthenium-catalyzed asymmetric transfer hydrogenation (ATH)
of levulinic acid (LA) to chiral γ-valerolactone (GVL). ATH
of LA has been explored with Noyori’s chiral catalyst (Ru–TsDPEN)
in methanol solvent. Efficacy of ATH reaction of LA was investigated
under different reactions conditions such as temperature, catalyst,
and hydrogen donor concentration. The effect of various organic tertiary
bases along with formic acid (FA) as a hydrogen donor was studied,
and N-methylpiperidine with FA (1:1 molar ratio)
was revealed as an efficient hydrogen donor for ATH of LA to GVL furnishing
chiral GVL with complete conversion and 93% enantiomeric excess (ee).
This operationally simple and mild ATH protocol was tested for practical
applicability of ATH of LA obtained from biomass waste (rice husk
and wheat straw) and furnished chiral GVL with 82% ee.
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