反应详情

温度

-78 °C

To an ice cold solution of 10.0 g (47.0 mmol) of 3-chloro-benzo[b]thiophene-2-carboxylic acid (1) in 200 mL of THF was added 47 mL of LiAlH4 (47 mmol, 1 M/THF). After 3 h, the reaction was quenched by addition of MeOH (ca. 40 mL). The volatiles were evaporated and the residue was treated with 50 mL 1 M HCl. After stirring for 10 min., the mixture was extracted with CH2Cl2 (3×150 mL). The combined CH2Cl2 solution was dried (MgSO4), filtered and evaporated. Purification by flash chromatography on silica gel (10→20% ethyl acetate/hexane) gave 4.32 g (21.6 mmol, 46%) of the alcohol (2). 3-Chloro-benzo[b]thiophene-2-carbaldehyde (3). A solution of alcohol 2 (4.32 g, 21.6 mmol) in 40 mL of CH2Cl2 was treated with 4A molecular sieves, NMO (3.81 g, 32.5 mmol), and TPAP (381 mg, 1.08 mmol). The reaction was stirred for 10 min. and then was evaporated to dryness. Purification by flash chromatography on silica gel (2% ethyl acetate/hexane) gave 3.52 g (18.3 mmol, 84%) of the aldehyde (3). (E)-3-(3-Chloro-benzo[b]thiophen-2-yl)-acrylic acid methyl ester (4). A solution of 3.52 g (18.3 mmol) of 3 in 50 mL toluene was treated with methyl(triphenylphosphoranylidene)acetate (7.48 g, 21.9 mmol). After 4 h, saturated NaHCO3 solution (50 mL) was added and the mixture was extracted with ethyl acetate (2×75 mL). The combined ethyl acetate solution was washed with brine (50 mL), dried (Na2SO4), filtered and evaporated. Purification by flash chromatography on silica gel (5% ethyl acetate/hexane) provided 3.60 g (14.6 mmol, 80%) of the enoate (4). 3-(3-Chloro-benzo[b]thiophen-2-yl)-propionic acid methyl ester (5). A solution of 3.60 g (14.6 mmol) of 4 in 50 mL THF was treated with Wilkinson's catalyst (3.35 g, 3.62 mmol). The mixture was stirred under 1 atm H2 for 18 h and then was filtered through celite. The solvent was evaporated and the residue was purified by flash chromatography on silica gel (0→2% ethyl acetate/hexane) to give 3.63 g (14.3 mmol, 99%) of the saturated ester (5). 3-(3-Chloro-benzo[b]thiophen-2-yl)-propan-1-ol (6). An ice cold solution of 3.63 g (14.3 mmol) of 5 in 60 mL of ether was treated with LiBH4 (621 mg, 28.5 mmol) and methanol (2 mL). After 30 min., 30 mL of 0.5 M NaOH solution was added. The mixture was extracted with ethyl acetate (2×25 mL) and the combined ethyl acetate solution was washed with brine (50 mL), dried (MgSO4), filtered and evaporated. The residue was purified by flash chromatography on silica gel (5→20% ethyl acetate/hexane) to give 2.57 g (11.3 mmol, 79%) of the alcohol (6). 3-(3-Chloro-benzo[b]thiophen-2-yl)-propionaldehyde (7). A −78° C. solution of oxalyl chloride (1.73 g, 13.6 mmol) in dichloromethane (20 mL) was treated with DMSO (20 mL). After 5 min., a solution of alcohol 6 (2.57 g, 11.3 mmol) in dichloromethane (20 mL) was added. After another 15 min., triethylamine (7.1 mL, 50.6 mmol) was added. The reaction was stirred at −78° C. for 5 min., and then was allowed to warm to room temperature. After 30 min., 100 mL water was added and the mixture was extracted with dichloromethane (3×60 mL). The combined dichloromethane solution was dried (Na2SO4), filtered and evaporated. Purification by flash chromatography on silica gel (10% ethyl acetate/hexane) gave 2.11 g (9.4 mmol, 83%) of the aldehyde (7). 5-(3-Chloro-benzo[b]thiophen-2-yl)-pent-1-yn-3-ol (8). A solution of aldehyde 7 (2.11 g, 9.4 mmol) in 15 mL THF was added to a solution of ethynylmagnesium bromide (28.2 mL, 14.1 mmol, 0.5 M THF) at 0° C. After 1.5 h, saturated NH4Cl solution (75 mL) was added and the mixture was extracted with ethyl acetate (3×50 mL). The combined ethyl acetate solution was washed with brine (50 mL) and then was dried (Na2SO4), filtered and evaporated. Purification by flash chromatography (5→20% ethyl acetate/hexane) gave 2.20 g (8.78 mmol, 93%) of the alcohol (8). tert-Butyl-{1-[2-(3-chloro-benzo[b]thiophen-2-yl)-ethyl]-prop-2-ynyloxy}-dimethyl-silane (9). A solution of alcohol 8 (2.20 g, 8.78 mmol) in dichloromethane (15 mL) was treated with DMAP (215 mg, 1.8 mmol), TBSCl (1.59 g, 10.5 mmol), and triethylamine (1.8 mL, 13.2 mmol). The reaction was stirred for 24 h and then saturated sodium bicarbonate solution (50 mL) was added. The mixture was extracted with dichloromethane (2×50 mL) and the combined dichloromethane solution was dried (Na2SO4), filtered and evaporated. Purification by flash chromatography (4% ethyl acetate/hexane) gave 3.06 g (6.4 mmol, 73%) of the protected alcohol (9). tert-Butyl-{(E)-1-[2-(3-chloro-benzo[b]thiophen-2-yl)-ethyl]-3-iodo-allyloxy}-dimethyl-silane (10). A solution of alkyne 9 (5.547 g, 15.2 mmol) in dichloromethane (50 mL) was treated with Cp2ZrHCl (5.794 g, 22.5 mmol). The reaction was stirred for 45 min. and then N-iodosuccinimide (4.966 g, 22.1 mmol) was added. After 15 min., saturated sodium bicarbonate solution (200 mL) was added and the mixture was extracted with dichloromethane (2×100 mL). The combined dichloromethane solution was dried (MgSO4), filtered and evaporated. Purification by flash chromatography on silica gel (0%→5% ethyl acetate/hexanes) gave 6.608 g (13.1 mmol, 86%) of the vinyl iodide (10). (Z)-7-{(1R,2R,3R)-3-(tert-Butyl-dimethyl-silanyloxy)-2-[(E)-3-(tert-butyl-dimethyl-silanylox)-5-(3-chloro-benzo[b]thiophen-2-yl)-pent-1-enyl]-5-oxo-cyclopentyl}-hept-5-enoic acid methyl ester (12, scheme 2). A −78° C. solution of iodide 10 (scheme 2, 2.305 g, 4.6 mmol) in THF (10 mL) was treated dropwise with t-butyllithium (5.9 mL, 10.0 mmol, 1.7 M/pentane). After stirring for 30 minutes, the red mixture was treated with lithium 2-thienylcyanocuprate (18.4 mL, 4.6 mmol, 0.25 M/THF, Aldrich). The resulting brown mixture was stirred in an ice bath for 10 minutes and then was cooled back down to −78° C. At this time, a solution of enone 11 (1.63 g, 4.6 mmol) in THF (5.0 mL) was added dropwise by cannula and the resulting mixture was stirred for 30 minutes at −78° C., 30 minutes at 0° C. and then 30 min. at room temperature.

1. stirringThe resulting brown mixture was stirred in an ice bath for 10 minutes
2. stirringthe resulting mixture was stirred for 30 minutes at −78° C., 30 minutes at 0° C.
3. custom30 min.
4. customat room temperature