Mrf 400

Experimental procedures and details, NMR spectra, and computational and crystallographic details can be found in the Supporting Information. In addition, NMR and computational data files can be obtained from the 4TU database under DOI: 10.4121/20015018.
Deposition Number(s) 2160732 (for 2) and CCDC 2160733 (for 5) contain the supplementary crystallographic data for this paper. These data are provided free of charge by the joint Cambridge Crystallographic Data Centre and Fachinformationszentrum Karlsruhe Access Structures service.
Procedure for the semi‐hydrogenation of internal alkynes: 0.60 mL of a stock solution of complex 3 (2.5 μmol/0.60 mL) in C₆D₆ was added to the alkyne substrate (50 μmol, 20 equiv). The solutions were then transferred to J. Young valved NMR tubes and mesitylene (internal standard, 3.0 μL) was added. The mixtures were degassed by three freeze‐pump‐thaw cycles and filled with H₂ (1 atm). The mixtures were placed in an oil bath at 25 °C (or 40 °C for some experiments) and the quantitative NMR spectra were collected after 24 h or 48 h (using an acquisition time of 5 sec and a relaxation time between scans set at 20 sec). Spectroscopic yields were determined with mesitylene as the internal standard. NMR data was recorded on an Agilent MRF 400 equipped with a OneNMR probe and Optima Tune system or a Varian VNMR−S‐400 equipped with a PFG probe at 298 K.

For the identification of 6-methoxy-4,6-dioxohexanoic acid, the accumulated product of ∆omeA grown on vanillic acid was isolated through ethyl acetate extraction. The organic phase was dried, dissolved in acetonitrile and analyzed for the presence of 6-methoxy-4,6-dioxohexanoic acid by HPLC. For NMR analysis, the aqueous sample was washed three times with CDCl₃. The aqueous layer was concentrated to dryness in vacuo (50 °C) and redissolved in D₂O. The ¹H-NMR spectrum was recorded on an Agilent MRF 400 equipped with a OneNMR probe and Optima Tune system. The signals of the major species correspond to 6-methoxy-4,6-dioxohexanoic acid (bisdeuterated at C5). The recorded spectrum is in good agreement with spectral data reported in the literature for the proposed structure [29 (link)].