S2 General Remarks Solvents for moisture-sensitive reactions were distilled and dried according to standard procedures. Anhydrous Na 2 SO 4 was used to dry organic solutions during workups. Reagents were purchased in the highest available commercial quality and used as supplied. Reactions were monitored by TLC with pre-coated silica gel 60 F254 aluminum plates (Merck KGaA, Darmstadt) using UV light as the visualizing agent and by dipping the plate into a solution of (NH 4 ) 6 Mo 7 O 24 .4 H 2 O

more »

... (12.5 g) and Ce(SO 4 ) 2 .4 H 2 O (5 g) in 10% aqueous H 2 SO 4 (500 mL), followed by heating. Flash column chromatography was performed with silica gel (0.035-0.070 mm, 60 Å) from Merck. Concentrations were carried out in a rotary evaporator. 1 H, 13 C, DEPT and 2D NMR were recorded using either Bruker DPX-250, AMX-300 and WM-500 spectrometers, or Varian Mercury 300 and Inova 400 spectrometers, as indicated; chemical shifts are reported in ppm and coupling constants in Hz; multiplicities are given as follows: s (singlet), br s (broad singlet), br d (broad doublet), d (doublet), t (triplet), and m (multiplet). Mass spectra were recorded on Micromass Autospec, TRACE MS and HP-5988-A spectrometers using Electronic Impact (EI, 70 eV), Electrospray (ESI) or Chemical Ionization (CI). Melting points were determined on a Büchi apparatus (Dr. Tottoli, Flawil, Switzerland).