烯烃的环氧化

案例

A 500-mL, three-necked, round-bottomed flask equipped with an overhead mechanical stirrer, a 125-mL addition funnel, and a thermocouple is charged with indene ((Note 1), 29.0 g, 0.25 mol, 1 equiv), dichloromethane (CH2Cl2) (30 mL), (S,S)-(N,N')-bis(3,5-di-tert-butylsalicylidene)-1,2-cyclohexanediaminomanganese(III) chloride (0.953 g, 1.5 mmol, 0.6 mol% , (Note 2)), and 4-phenylpyridine N-oxide ((Note 3), 1.28 g, 7.5 mmol, 3.0 mol%) under a nitrogen (N2) atmosphere. The resulting brown mixture is cooled to −5°C, and then a cold sodium hypochlorite (NaOCl) solution (191 mL, 1.7 M, 1.3 equiv, (Note 4)) is added slowly with vigorous stirring while maintaining the reaction temperature between 0°C and 2°C (Note 5). Upon complete addition of the bleach, the reaction is stirred for an additional 1 hr at 0°C. At this point, hexanes (200 mL) are added in one portion with stirring, and the reaction mixture is filtered through a pad of Celite on a large Büchner funnel. The filter cake is washed with dichloromethane (2 × 50 mL), and the filtrate is transferred to a 500-mL separatory funnel. The lower aqueous layer is removed, and the brown organic layer is washed with aqueous saturated sodium chloride (NaCl) solution (100 mL). The organic layer is dried over sodium sulfate (Na2SO4), filtered, and concentrated by rotary evaporation. A small amount of calcium hydride (CaH2) (100 mg) is added to the brown residue, and the epoxide is isolated by short path vacuum distillation, bp 58-60°C (0.025 mm), to yield 24.0 g of epoxyindane (84-86% ee) as a colorless to slightly yellow liquid (0.197 mol, 71% yield, (Note 6), (Note 7), and (Note 8)).

Org. Synth. 1999, 76, 46

案例

A 250-mL, round-bottomed flask, equipped for magnetic stirring and with a condenser fitted with a calcium chloride drying tube, is charged with 9.76 g (40 mmol) of 1,1,1-trifluoro-2-ethoxy-5-phenyl-2-pentene , and a solution of 14.79 g (60 mmol) of 70% meta-chloroperoxybenzoic acid in 170 mL of dichloromethane (Note 10) and (Note 11). The resulting mixture is heated under reflux with stirring for 20 hr (Note 12), cooled, and concentrated to 50-60 mL under reduced pressure. The residual liquid is diluted with 200 mL of pentane and the supernatant liquid from the resulting suspension is passed through a short silica gel column (Note 8). The residual solids are washed twice with 50 mL of a 10:1 mixture (v/v) of pentane-diethyl ether , and the wash solutions are passed through the same column. The column is then eluted with 100 mL of a 5:1 (v/v) mixture of pentane-diethyl ether . The combined eluants are concentrated under reduced pressure and the residual liquid is purified by bulb-to-bulb vacuum distillation (oven temperature 120-130°C at 10 mm) to provide 9.36-9.88 g (90-95%) of pure 1,1,1-trifluoro-2-ethoxy-2,3-epoxy-5-phenylpentane (4) as a clear, colorless liquid, bp 90°C (10 mm)

Org. Synth. 1998, 75, 153

案例

A 500-mL, 1-neck round-bottom flask equipped with a Teflon-coated magnetic stir bar was oven dried and then fitted with a serum cap and flushed with nitrogen. The flask was charged with 200 mL of dry (distilled from CaH₂ ) reagent-grade dichloromethane and cooled by stirring in a -23 °C bath Then the following liquids were added sequentially via syringe while stirring in the cooling bath: 5.94 mL (5.68 g, 20 mmol) of Ti(OiPr)₄; 3.43 mL (4.12 g, 20 mmol ) of L(+)-diethyl tartrate (used as received from Aldrich), stirred 5 min before next addition; 3.47 mL (3.08 g, 20 mmol) of geraniol (Aldrich Gold Label); and, finally, ca. 11 mL of a dichloromethane solution (3.67 M in TBHP) containing ca. 40 mmol(2 equiv) of anhydrous tert-butyl hydroperoxide (TBHP).

The resulting homogeneous solution was then stored overnight (ca. 18 h) at ca. -20 °C in the sealed (serum cap) reaction vessel (the progress of the epoxidation can be monitored by TLC ) . Then the flask was placed in a -23 °C bath (dry and 50 mL of 10% aqueous tartaric acid solution was added while stirring; the aqueous layer solidified. After 30 min, the cooling bath was removed and stirring was continued at room temperature for 1 h or until the aqueous layer became clear. After separation of the aqueous layer, the organic layer was washed once with water, then dried over Na₂SO₄, and concentrated to afford a colorless oil with an odor revealing contamination by TBHP.

This oil was diluted with 150 mL of ether, and the resulting solution was cooled in an ice bath, and then 60 mL of 1 N sodium hydroxide solution was added. This produced a two-phase mixture which was stirred at 0 °C for 30min, The ether phase was washed with brine, dried over Na₂SO₄,and concentrated to give 4.24 g of a clear oil. Chromatography on silica gel afforded of 2(S),3(S)-epoxygeraniol (2.6 g, 77%), Analysis of this material as the "MTPA ester” gave an enantiomeric excess (ee) of >95% whereas analysis of the derived epoxy acetate by using Eu(hfbc)₃ chiral shift reagent gave 94% ee.

JACS, 1980, 102, 5974

案例

Aqueous Na₂EDTA (1x10^-4M, 10 mL) and a catalytic amount of tetrabutylammonium hydroxide were added to a solution of trans-stilbene (0.18 g, 1 mmol) in acetonitrile (15 mL) with vigorous stirring at 0 °C. A mixture of Oxone^TM (3.07 g, 5 mmol) and sodium bicarbonate (1.3 g, 15.5 mmol) was pulverized. A small portion of this mixture was added to the reaction mixture to bring the pH to >7. After 5 min, fructose derived ketone (0.77 g, 3 mmol) was added portionwise over a period of 1 h. Simultaneously, the rest of Oxone^TM and sodium bicarbonate was added portionwise over 50 min. After completion of the addition of ketone 3, the reaction mixture was stirred for another 1 h at 0 °C, diluted with water (30 mL) and extracted with n-hexane (4x40 mL). The combined extracts were washed with brine, dried (Na₂SO₄ ), filtered, concentrated, and purified by flash chromatography (the silica gel was buffered with 1% triethylamine solution in hexanes; hexanes/ether (1/0 to 50/1) was used as the eluent) to afford 0.149 g (73%) trans-stilbene oxide as white crystals.

JACS, 1980, 102, 5974