Purified triflate

After 20 min, HMPA (6.0 mmol, 0.6 mL) and A-phenyltrifluoromethanesulphonamide (2.6 mmol, 0.6 g) in THF (5 mL) were added and the solution was allowed to warm to room temperature. The reaction mixture was stirred for 4 h and then heated with 1 1 solution of saturated aqueous NH4CI/NH4OH (20 mL), exhacted with ethyl acetate (3x20 mL), dried, evaporated and the residue was purified by flash silica gel chromatography using hexane as eluent affording the vinyl triflates. 

The residue was purified by silica gel chromatography (hexane-ethyl acetate, 30 1) to give the corresponding triflate (310.0 mg, 72%) as an oil, which was immediately used for the next cross-coupling reaction. 

A -Acetyltyrosine methyl ester (400 mg, 1.68 mmol) and 3,5-dichloro-l-fluoropyridinium triflate (lm 632 mg, 2 mmol) were stirred under N2 in dry CH2Cl2/MeCN (10 mL, 9 1). After 8 h the starting material and reagent were consumed. The reaction mixture was poured into H20 (10 mL), neutralized with NaHC02, and separated. The organic layer was washed with H20 (10 mL), dried (Na2S04) and concentrated under reduced pressure. The crude product was purified by vacuum column chromatography (silica gel, 60% EtOAc/petroleum ether, bp 35-60 JC) yield 280 mg (65%). 

Hydroxyestra-l,3,5(10)-trien-17-one (500mg, 1.85 mmol) and 1-fluoropyridinium triflate (la 915 mg, 3.7 mmol) in 1,1,2-trichloroethane (8mL) were refluxed under N2 for 24 h. Solvent was removed under reduced pressure, and the residue poured into H20 and extracted with CH2C12. Evaporation of the dried (MgS04) extract yielded a brown oil which was acetylated. The crude mixture of 16 and 17 was partially purified by flash column chromatography (petroleum ether bp 60-80°C/EtOAc9 1 to 7 3). Theco-eluted isomers were separated by fractional recrystallization (petroleum ether bp 60-80 C/abs EtOH 2 8) 16 was obtained as first crop yield 325 mg (53 %) mp 88 - 90 C and 17 as colorless crystals yield 123 mg (20%) mp 97-99°C. 

To a mixture of phenol 21(3 (70.4 mg, 0.216 mmol) and Et3N (28.4 mg, 0.281 mmol) in CH2C12 (3 mL) was added Tf20 (91.3 mg, 0.324 mmol) at 0°C. The reaction was terminated immediately by adding saturated aqueous NaHCOj, and the mixture was extracted with CH2C12. The combined organic layer was washed with brine and then dried over NajSO After removal of the solvent in vacuo, the residue was purified by silica gel PTLC (hexane-EtOAc, 5 5) to affoid triflate 22 (96.0 mg, 97.1%). 

It is not only that catalyst 82 is more easily prepared than 4 more importantly, as illustrated in Scheme 19, a solution of 82, obtained by the reaction of commercially available reagents bis(potassium salt) 83 and Mo triflate 84 (Strem), can be directly used to promote enantioselective metathesis. Similar levels of reactivity and selectivity are obtained with in situ 82 as with isolated and purified 4a or 82 (cf. Scheme 19). Moreover, asymmetric olefin metatheses proceed with equal efficiency and selectivity with the same stock solutions of (R)-83 and 84 after two weeks. The use of a glovebox, Schlenck equipment, or vacuum lines is not necessary (even with the two-week old solutions). 

The Suzuki coupling reaction is a powerful tool for carbon-carbon bond formation in combinatorial library production.23 Many different reaction conditions and catalyst systems have been reported for the cross-coupling of aryl triflates and aromatic halides with boronic acids in solution. After some experimentation, we found that the Suzuki cleavage of the resin-bound perfluoroalkylsulfonates proceeded smoothly by using [l,l -bis (diphenylphosphino)ferrocene]dichloropalladium(II), triethylamine, and boronic acids in dimethylformamide at 80° within 8 h afforded the desired biaryl compounds in good yields.24 The desired products are easily isolated by a simple two-phase extraction process and purified by preparative TLC to give the biaryl compounds in high purity, as determined by HPLC, GC-MS, and LC-MS analysis. 

The stable (arylsulfonylmethyl)iodonium salts 49 and 50 can be conveniently prepared in two steps starting from the readily available iodomethyl sulfones 47 (Scheme 23) [41]. Iodonium salts 49 and 50 are not moisture sensitive, can be purified by crystallization from acetonitrile, and can be stored for several months in a refrigerator. The structure of iodonium triflate 50 was unambiguously established by a single crystal X-ray analysis [41]. 

Toward this end, Woerpel and Nevarez examined the possibility of di-tert-butylsilylene transfer from cyclohexene silacyclopropane 58 to imine 169a (Scheme 7.48).123 Thermolysis produced a mixture of silaaziridine 170a and an imine-dimer byproduct (171). The results by Brook and coworkers suggested that if the temperature of silylene transfer were lowered, isolation of 170a without formation of byproduct 171 would be possible. As anticipated, exposure of cyclohexene silacyclopropane 58 to imine 169a in the presence of substoichiometric amounts of silver triflate produced only 170a. This silaazridine could be purified by bulb-to-bulb distillation to afford the product in 80% yield. Copper salts required... 

A dry two-neck flask was charged with amine (1.00 mmol), triflate or bromide (1.20 mmol), base (1.40 mmol), ligand (10 mol%), palladium acetate (Pd(OAc)2) or tris-(dibenzylidene-acetone)dipalladium (0) (Pd2dba3) (5 mol%), and toluene (2.00 mL/mmol of amine). The reaction was flushed with N2 and heated at 80 °C. The mixture was diluted with ether, filtered through a pad of Celite, and the volatile components were removed reduced pressure to give a crude product, which was purified by flash column chromatography on silica gel. 

A mixture of cubyl iodide (1 mmol), IOB (3 mmol) and trimethylsilyl triflate (666 mg, 3 mmol) in dry dichloromethane was stirred at room temperature for 1 h to several days, depending on the substituent X the following order was noted, concerning reaction time H < Me < C02Me < Br,I,Cl. After the usual work up, the residues were purified by flash chromatography (with pentane) or microdistillation to give the pure products in 50-60% yield. 

The iodonium triflate (460 mg, 1 mmol) was added to a stirred slurry of anhydrous sodium p-toluene sulphinate (180 mg, 1.01 mmol) in dichloromethane (15 ml) at 20°C under nitrogen. After 15 min water (10 ml) was added and the phases were separated the aqueous layer was extracted with additional dichloromethane (2 x 5 ml), and the combined organic extracts were dried. The filtered solution was treated with hexanes (30 ml) and concentrated. The solid residue was purified by radial chromatography (silica gel, 200-400 mesh, dichloromethane-hexanes) to afford 3-tosyl-bicyclo[3.2.0]-3-heptene-2-one (197 mg, 75%), m.p. 164-165°C. The method is general for the preparation of sulphones with a cyclopentenone moiety other alkenyl iodonium salts gave alkynyl sulphones with sulphinates (Section 9.4.4). 

A mixture of 0.55 g (1.8 mmol) of phenylselenyl triflate and 0.18 g (1.8 mmol) of 3-methyl-4-penten-l-ol (5) in 32 mL of CH2C12 is stirred at 0°C for 15 min. After dilution with 50 mL of Et20, the organic layer is washed with sat. brine. Drying over MgS04 and removal of the solvent leaves a residue which is purified by column chromatography (silica gel, petroleum cther/EtOAc 9 1) yield 0.369 g (79%) d.r. (trans lets) 80 20. The structures of the trans- and cw-isomers are confirmed by differential NOE 1H NMR at 500 MHz. 

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