General InformationAll reactions were carried out under air atmosphere unless otherwise noted. All reagents and solvents were obtained from commercial suppliers and used without further purification. Reactions were monitored by TLC on silica gel plates (GF254). 1 H NMR and 13 C NMR spectra were recorded on 400 MHz spectrometer, with chemical shifts (δ) referenced to the residual solvent signal ( 1 H and 13 C) or referenced externally to H 3 PO 4 (0 ppm). Chemical shifts (δ) are reported in ppm downfield from tetramethylsilane. Abbreviations for signal couplings are: s, singlet; d, doublet; t, triplet; m, multiplet.
MaterialsSolvents such as toluene, Et 2 O and THF were dried and distilled over Na / benzophenone ketyl and stored under argon atmosphere. EtOH and MeOH were dried and distilled over magnesium and stored under argon atmosphere. Anisole, CH 2 Cl 2 , hexane, and ethyl acetate were commercially available without further purification prior to use. All substrates were used without further purification. KReO 4 was purchased from ZHUZHOUKAITE Industrial Corporation. Ltd. [1] , ReH 7 (PCy 3 ) 2
Synthesis of heptahydridobis(tricyclohexylphosphine)rheniumReOCl 3 (PCy 3 ) 2 (2.3 mmol, 2.0 g) and NaBH 4 (80 mmol, 3.0 g) were added to 130 mL of absolute ethanol and the mixture was stirred until the color of solvent turned into beige. After the reaction finished, the solvent was removed on a vacuum line. The residue was washed twice with absolute water (50 mL), twice with EtOH (50 mL), and twice times with Et 2 O (20 mL). The dry residue was extracted three times with THF (20 mL). The volume of THF was reduced to 10 mL. Et 2 O (30 mL), and hexane (30 mL) were added to induced precipitation. The beige microcrystalline ReH 7 (PCy 3 ) 2 was corrected by filtering, washed with Et 2 O (20 mL), and dried under vacuum. Recrystallization from THF-Hexane gave a white compound. Yield 0.91g (52 %).
General procedure for the rhenium-catalyzed dehydrogenative coupling of alcohols and carbonyl compoundsThe mixture of carbonyl compound 1 (0.2 mmol), alcohol 2 (0.8 mmol), ReH 7 (PCy 3 ) 2 (5 mol%, 8 mg) and anhydrous LiCl (0.4 mmol, 17 mg) were added into the flask. The flask was evacuated and backfilled with N 2 . Then, anisole (0.5 mL) was added. The reaction mixture was vigorously stirred at 150 o C under an atmosphere of N 2 for 20-36 h. After the reaction finished, the reaction mixture was cooled to room temperature and extracted with ethyl acetate (3 × 5 mL), the combined organic phases were dried over anhydrous Na 2 SO 4 and the solvent was evaporated under vacuum. After removing the solvents in vacuum, the residue was purified by flash column chromatography on silica gel or preparative TLC on GF254 to afford the desired products 3. The ratio of E/Z was detected by 1 H NMR spectroscopy. E-isomer as main product was separated and characterized.
General procedure for the rhenium-catalyzed dehydrogenative oxidation of alcoholsIn a round bottom flask, the alcohol 2 (0.2 mmol), ReH 7 (PCy 3 ) 2 (5 mol%, 8 mg) and anisole (0.5 ml...