Fig. 2. Summary of this work.

(A) Renewable carbon feedstocks that afford various 1,4-BDO derivatives and 1,2-propanediol. Compound names in blue are Krebs cycle metabolites, while those marked with asterisks are possible feedstocks listed as top 30 value-added chemicals in the initial U.S. Department of Energy/the National Renewable Energy Laboratory report in 2004 (1). Succinic acid (SucA), malic acid (MliA), aspartic acid (AspA), oxaloacetic acid (OacA), tartaric acid (TarA), fumaric acid (FumA), maleic acid (MleA), maleic anhydride (MleAn), succinic anhydride (SucAn), γ-butyrolactone (GBL), itaconic acid (ItaA), 2-oxoglutaric acid (OglA), levulinic acid (LevA), aconitic acid (AcoA), and citric acid (CitA). (B) Single-crystal x-ray diffraction structure of Ir-a (left; Et₂O included). Color key: Ir (blue), N (purple), P (orange), Cl (green), O (red), and H (white). See also fig. S1. [BPh₄]⁻ is omitted for clarity. Ir and Ru complexes for hydrogenation tested in this work (right).