Tetrahydrofuran complexes Subject

Among the O-containing heterocyclic ligands, tetrahydrofuran (THF) 376 is the subject of permanent interest [13]. As a result of its interaction (3.18) with metal salts, the molecular solvent complexes of the type 298 (Sec. 2.2.4.4) and 577 are formed, and can be used as precursors to obtain coordination compounds with other ligand systems ... 

The oxidative functionalization of olefins mediated by transition metal oxides leads to a variety of products including epoxides, 1,2-diols, 1,2-aminoalcohols, and 1,2-diamines [1]. Also the formation of tetrahydrofurans (THF) from 1,5-dienes has been observed, and enantioselective versions of the different reactions have been developed. Although a lot of experimental data has been available, the reaction mechanisms have been a subject of controversial discussion. Especially, osmium (VIII) complexes play an important role there, as the proposal of a stepwise mechanism [2] for the dihydroxylation (DH) of olefins by osmium tetroxide (OSO4) had started an intense discussion about the mechanism [2—11],... 

Pentacarbonyliron (2.9 g, 15 mmol) is added dropwise to a solution of anhydrous potassium butoxide (1.68 g, 15 mmol) in tetrahydrofuran (70 mL) at 25 C under dry nitrogen. The color of the reaction mixture immediately changes from yellow to dark brown. The reaction mixture is stirred for another 1 h at 70 °C and brought slowly to 25 °C. Diphenylacetylene (0.44 g, 2.5 mmol) is added and further stirred for 10 h at 70 C. The mixture is brought slowly to 25 °C. The metal carbonyl complexes are oxidized using copper(II) chloride dihydrate (5.0 g, 30 mmol) in acetone (20 mL). Saturated sodium chloride solution is added and the contents are extracted with ether (2 x 75 mL), dried over anhydrous sodium sulfate, and concentrated under reduced pressure. The residue is subjected to column chromatography [silica gel, hexane (2%)/ethyl acetate] to afford the pure 3,4-diphenyl-3-cyclobutene-1,2-dione mp 95-96 °C, 0.52 g (88%) ... 

---