* All experimental methods are cited from the reference, please refer to the original source for details. We do not guarantee the accuracy of the content in the reference.
General procedure: A 25 mL round-bottomed flask was charged with 2-aryloxyacetaldehyde diethyl acetals (1 mmol), Sn-b (0.1 g), andtrifluorotoluene (10 mL). The mixture was stirred under refluxingcondition and monitored by GC. Upon completion, the mixture wascooled to room temperature, and the catalyst Sn-b was filtrate off.The filter cake was washed with trifluorotoluene (10 mL3). Thecombined filtratewas concentrated under vacuum. The residuewaspurified by flash column chromatography on SiO2 (petroleumether/ethyl acetate) to afford the desired 2,3-unsubstituted benzo[b]furans.
45%
With PPA In benzene for 2.5 h; Heating / reflux
To a mixture of benzene (200 ml) containing polyphosphoric acid (7.9 g, 0.035 mol) was added 2-(4-fluoro-phenoxy)-acetaldehyde diethyl acetal (8 g, 0.035 mol). The mixture was stirred vigorously while being heated to reflux for 2.5 hours. The reaction mixture was cooled to room temperature and decanted from the polyphosphoric acid. The solvent was removed under vacuum. Chromatography (5percent ethyl acetate-hexanes) afforded 3.4 g (45percent) of product as a clear oil: 1H NMR (CDCl3) δ 6.74 (dd, 1H, J = 2.0, 0.6 Hz), 7.01 (td, 1H, J = 9, 2.7 Hz), 7.25 (dd, 1H, J = 8.4, 2.7 Hz), 7.43 ( dd, 1H, J = 9, 3.9 Hz), 7.65 (d, 1H, J = 1.8 Hz).
Reference：
[1] Tetrahedron, 2015, vol. 71, # 29, p. 4835 - 4841
[2] Journal of Medicinal Chemistry, 2004, vol. 47, # 15, p. 3823 - 3842
[3] Patent: EP1147083, 2004, B1, . Location in patent: Page 35
[4] Journal of the American Chemical Society, 2017, vol. 139, # 24, p. 8267 - 8276
[5] European Journal of Organic Chemistry, 2016, vol. 2016, # 13, p. 2268 - 2273
[6] Journal of Medicinal Chemistry, 2004, vol. 47, # 7, p. 1609 - 1612
[7] Patent: EP1380576, 2004, A1, . Location in patent: Page 66
[8] Patent: WO2011/99010, 2011, A1, . Location in patent: Page/Page column 38
[9] Patent: US2012/225863, 2012, A1, . Location in patent: Page/Page column 17
[10] Patent: WO2012/119046, 2012, A2, . Location in patent: Page/Page column 65-66
[11] New Journal of Chemistry, 2016, vol. 40, # 8, p. 6564 - 6567
2
[ 371-41-5 ]
[ 24410-59-1 ]
Reference：
[1] Journal of Medicinal Chemistry, 2004, vol. 47, # 15, p. 3823 - 3842
[2] Journal of Medicinal Chemistry, 2004, vol. 47, # 7, p. 1609 - 1612
[3] Patent: US2012/225863, 2012, A1,
[4] Patent: WO2012/119046, 2012, A2,
[5] Patent: WO2015/42397, 2015, A1,
[6] Tetrahedron, 2015, vol. 71, # 29, p. 4835 - 4841
[7] European Journal of Organic Chemistry, 2016, vol. 2016, # 13, p. 2268 - 2273
[8] New Journal of Chemistry, 2016, vol. 40, # 8, p. 6564 - 6567
[9] Journal of the American Chemical Society, 2017, vol. 139, # 24, p. 8267 - 8276
3
[ 24410-59-1 ]
[ 5419-55-6 ]
[ 473416-33-0 ]
Yield
Reaction Conditions
Operation in experiment
26%
Stage #1: With n-butyllithium; N,N,N,N,-tetramethylethylenediamine In tetrahydrofuran; hexane at -60 - -10℃; for 75 h; Inert atmosphere Stage #2: at -60 - 20℃; Inert atmosphere Stage #3: With hydrogenchloride; water In tetrahydrofuran; hexane
Step 3. 5-Fluorobenzofuran-2-ylboronic acid To a solution of 5-fluorobenzofuran (10 g, 73.53 mmol) in dry tetrahydrofuran (250 mL) was added tetramethylethylenediamine (10.2 g, 87.93 mmol). The solution was kept below -60° C. under nitrogen, while BuLi (93.75 mmol, 2.5M solution in hexane) was added dropwise. It was warmed to -10° C. during 45 min and stirred at this temperature for another 30 min. The mixture was cooled again below -60° C. followed by dropwise addition of triisopropyl borate (41.4 g, 220.21 mmol). After warming to room temperature the mixture was quenched with hydrochloric acid (70 mL, 2N) and stirred for 1 h. The alkaline aqueous layer was brought to pH 5 and extracted with ethyl acetate (3.x.80 mL). All organic layers were combined, dried over sodium sulfate, and concentrated in vacuo to give 5-fluorobenzofuran-2-ylboronic acid (3.5 g, 26percent) which was used for the next step without further purification.1H-NMR (300 MHz, CDCl3): δ 8.63 (s, 2H), 7.58-7.62 (m, 1H), 7.44-7.49 (m, 2H), 7.15-7.22 (m, 1H)
With tin-exchanged H-b zeolite (Sn-b); for 1.5h;Reflux;
General procedure: A 25 mL round-bottomed flask was charged with 2-aryloxyacetaldehyde diethyl acetals (1 mmol), Sn-b (0.1 g), andtrifluorotoluene (10 mL). The mixture was stirred under refluxingcondition and monitored by GC. Upon completion, the mixture wascooled to room temperature, and the catalyst Sn-b was filtrate off.The filter cake was washed with trifluorotoluene (10 mL3). Thecombined filtratewas concentrated under vacuum. The residuewaspurified by flash column chromatography on SiO2 (petroleumether/ethyl acetate) to afford the desired 2,3-unsubstituted benzo[b]furans.
45%
With PPA; In benzene; for 2.5h;Heating / reflux;
To a mixture of benzene (200 ml) containing polyphosphoric acid (7.9 g, 0.035 mol) was added 2-(4-fluoro-phenoxy)-acetaldehyde diethyl acetal (8 g, 0.035 mol). The mixture was stirred vigorously while being heated to reflux for 2.5 hours. The reaction mixture was cooled to room temperature and decanted from the polyphosphoric acid. The solvent was removed under vacuum. Chromatography (5% ethyl acetate-hexanes) afforded 3.4 g (45%) of product as a clear oil: 1H NMR (CDCl3) delta 6.74 (dd, 1H, J = 2.0, 0.6 Hz), 7.01 (td, 1H, J = 9, 2.7 Hz), 7.25 (dd, 1H, J = 8.4, 2.7 Hz), 7.43 ( dd, 1H, J = 9, 3.9 Hz), 7.65 (d, 1H, J = 1.8 Hz).
With amberlyst 15; In hexane; at 20 - 200℃; for 11h;
To a solution of 16.0 g of 1-(2,2-diethoxyethoxy)-4-fluorobenzene in 50 ml n-hexane was added 3.2 g of amberlyst 15 at room temperature. After the mixture was treated in a sealed tube at 200C for 11 hours, the amberlyst 15 was filtered off. The solvent was evaporated, and the crude product was purified and separated by silica gel column chromatography (n-hexane), to give 4.8 g of the title compound as a colorless oil.1H-NMR (400 MHz, CDCl3) d 6.74 (1H, dd, J = 1.2, 2.4 Hz), 7.02 (1H, dt, J = 2.4, 8.8 Hz), 7.25 (1H, dd, J = 2.4, 8.8 Hz), 7.41 - 7.44 (1H, m), 7.65 (1H, d, J = 2.4 Hz).
Amberlyst 15; In toluene; at 120℃;Reflux;
EXAMPLE 6Preparation of 5-substituted benzofuranThe l-substituted-4-(2,2-diethoxyethoxy)benzene (100 mmol) was refluxed in dry toluene (30 ml) with Amberlyst 15 (2.5 g) at 120C for 6-8 h with concomitant removal of the azeotrope using a Dean-Stark apparatus. The resulting reaction mixture was filtered and the resin was washed with an excess of toluene. The combined filtrates were concentrated to dryness under reduced pressure and the resulting compounds were purified by crystallization, by distillation or by silica gel column chromatography. The following 5-substituted benzofurans were prepared by described above method: 5-Fluorobenzofuran, oil
With polyphosphoric acid; In benzene; for 2.5h;Reflux;
Step 2. 5-Fluorobenzofuran To a mixture of benzene (200 mL) containing polyphosphoric acid (80 g, 236.69 mmol) was added 2-(4-fluoro-phenoxy)-acetaldehyde diethyl acetal (45 g, 197.37 mmol). The mixture was stirred vigorously while being heated to reflux for 2.5 hours. The reaction mixture was cooled to room temperature and decanted from the polyphosphoric acid. The solvent was removed under vacuum to give the residue, which was purified by a silica gel column (1% ethyl acetate in petroleum ether) to afford 5-fluorobenzofuran as colorless oil (14.0 g, crude).1H-NMR (300 MHz, CDCl3): delta 7.67 (d, J=2.1 Hz, 1H), 7.44-7.48 (m, 1H), 7.27-7.30 (m, 1H), 7.01-7.08 (m, 1H), 6.76-6.77 (m, 1H)
With polyphosphoric acid; In benzene; for 2.5h;Reflux;
Step 2. 5-FluorobenzofuranTo a mixture of benzene (200 mL) containing polyphosphoric acid (80 g, 236.69 mmol) was added 2-(4-fluoro-phenoxy)-acetaldehyde diethyl acetal (45 g, 197.37 mmol). The mixture was stirred vigorously while being heated to reflux for 2.5 hours. The reaction mixture was cooled to room temperature and decanted from the polyphosphoric acid. The solvent was removed under vacuum to give the residue, which was purified by a silica gel column with 1% ethyl acetate in petroleum ether to afford 5-fluorobenzofuran as colorless oil (14.0 g, crude). 'H-NMR (300 MHz, CDCI3): delta 7.67 (d, / = 2.1 Hz, 1H), 7.44 - 7.48 (m, 1H), 7.27 - 7.30 (m, 1H), 7.01- 7.08 (m, 1H), 6.76 - 6.77 (m, 1H)
With hydrogen;palladium 10% on activated carbon; In acetic acid; under 2585.81 Torr; for 12h;
A solution of <strong>[24410-59-1]5-fluorobenzofuran</strong> and 10% palladium on carbon in acetic acid (25 ml) was hydrogenated under 50 psi for 12 hours. The catalyst was filtered through celite and the celite was washed with methylene chloride (200 ml). The organic layer was washed sequentially with 1N NaOH (3 x 100 ml), brine (3 x 100 ml) and dried over anhydrous sodium sulfate and filtered. The solvent was removed under vacuum to afforded 2.59 g (85%) of product as a clear oil: 1H NMR (300 MHz, CDCl3): delta 3.12 (t, 2H, J = 8.7 Hz), 4.58 (t, 2H, J = 8.7 Hz), 6.68 (dd, 1H, J = 8.7, 4.2 Hz), 6.79 (tm, 1H, J = 8.7 Hz), 6.89 (dm, 1H, J = 8.1 Hz).
With n-butyllithium; In tetrahydrofuran; hexane; at -78 - 20℃; for 3.33333h;
In a nitrogen atmosphere, to a solution of 2.0 g of <strong>[24410-59-1]5-fluorobenzofuran</strong> in 150 ml tetrahydrofuran was added 18.5 ml of a 1.59 M solution of n-butyllithium in n-hexane at-78C, and the mixture was stirred at the same temperature for 10 minutes and at 0C for further 10 minutes. At -78C, 3.7 ml of triethoxyborane was added, and the mixture was stirred for 2 hours while elevating to 0C. 30 ml of 1 N hydrochloric acid was added, stirred at room temperature for 1 hour, and then the mixture was extracted with ethyl acetate. The extract was washed with brine, dried over anhydrous magnesium sulfate and the solvent was evaporated. The crude product was purified and separated by silica gel column chromatography (ethyl acetate:n-hexane = 1:3 to 1:1), to give 525 mg of the title compound as colorless crystals.1H-NMR (400 MHz, CDCl3) d 7.09 (1H, dt, J = 2.4, 8.8 Hz), 7.29 (1H, dd, J = 2.4, 8.8 Hz), 7.33 (1H, s), 7.44 (1H, dd, J = 4.0, 8.8 Hz).
Butyllithium (1.5 mL, 2.4 mmol, 1.6 M) was added at -75 C. to a solution of <strong>[24410-59-1]5-fluorobenzofuran</strong> (0.3 g, 2.2 mmol) in THF (10 mL). Tributyltin chloride (0.98 g, 1 mL) was added at -75 C. and the mixture was allowed to warm to 25 C. over a period of 2 hours. Water (25 mL) was added and the aqueous layer was extracted with diethyl ether (2×25 mL). The combined organic extracts were dried over Na2SO4 and concentrated. Silica gel chromatography (pentane) provided tributyl-(<strong>[24410-59-1]5-fluorobenzofuran</strong>-2-yl)-stannane (210 mg).
Step 3. <strong>[24410-59-1]5-Fluorobenzofuran</strong>-2-ylboronic acid To a solution of <strong>[24410-59-1]5-fluorobenzofuran</strong> (10 g, 73.53 mmol) in dry tetrahydrofuran (250 mL) was added tetramethylethylenediamine (10.2 g, 87.93 mmol). The solution was kept below -60 C. under nitrogen, while BuLi (93.75 mmol, 2.5M solution in hexane) was added dropwise. It was warmed to -10 C. during 45 min and stirred at this temperature for another 30 min. The mixture was cooled again below -60 C. followed by dropwise addition of triisopropyl borate (41.4 g, 220.21 mmol). After warming to room temperature the mixture was quenched with hydrochloric acid (70 mL, 2N) and stirred for 1 h. The alkaline aqueous layer was brought to pH 5 and extracted with ethyl acetate (3×80 mL). All organic layers were combined, dried over sodium sulfate, and concentrated in vacuo to give <strong>[24410-59-1]5-fluorobenzofuran</strong>-2-ylboronic acid (3.5 g, 26%) which was used for the next step without further purification.1H-NMR (300 MHz, CDCl3): delta 8.63 (s, 2H), 7.58-7.62 (m, 1H), 7.44-7.49 (m, 2H), 7.15-7.22 (m, 1H)
Step 3. <strong>[24410-59-1]5-Fluorobenzofuran</strong>-2-ylboronic acidTo a solution of <strong>[24410-59-1]5-fluorobenzofuran</strong> (10 g, 73.53 mmol) in dry tetrahydrofuran (250 mL) were added tetramethylethylenediamine (10.2 g, 87.93 mmol). The solution was kept below - 60C under nitrogen, while BuLi (93.75 mmlo, 2.5M solution in hexane) was added drop wise. It was warmed to -10C during 45 min and stirred at this temperature for another 30 min. The mixture was cooled again below -60C followed by dropwise addition of triisopropyl borate (41.4 g, 220.21 mmol). After warming to room temperature the mixture was quenched with hydrochloric acid (70 mL, 2N) and stirred for 1 h. The alkaline aqueous layer was brought to pH 5 and extracted with ethyl acetate (3 x 80 mL). All organic layers were combined, dried over sodium sulfate, and concentrated in vacuo to give 5- fluorobenzofuran-2-ylboronic acid (3.5 g, 26%) which was used for the next step without further purification.'H-NMR (300 MHz, CDCI3): delta 8.63 (s, 2H), 7.58 - 7.62 (m, 1H), 7.44 - 7.49 (m, 2H), 7.15 - 7.22 (m, 1H)
Step 1: At -78C, 1.2 mL (1.93 mmol) of a 1.6 M solution of n-butyllithium were slowly added to 175 mg (1.29 mmol) <strong>[24410-59-1]<strong>[24410-59-1]5-fluorobenzofuran</strong>e</strong> in 10 mL anhydroustetrahydrofurane. The mixture was stirred for 1 h at -78C. 0.52 mL (1.93 mmol) tri-n-buty[tinch[oride was added at -78C. The cooling bath was removed and stirring was continued for 72 h.Methanol was carefully added and the solvent evaporated. The obtained mixture was adsorbed on isolute and purified by flash chromatography. The obtainedmaterial (336 mg) was used directly in the subsequent step 2.Step 2: A mixture of 165 mg of the product from step 1, 100 mg (0.3 mmol) of intermediate 111.1 5, 10.5 mg (0.015 mmol) bis(triphenylphosphine)palladium(II) and 5.7 mg (0.03 mmol) copper(I)iodide in tetrahydrofurane were refluxed for 16 h.The reaction mixture was filtered through a of pad celite. The filtrate wasevaporated and the precipitate was dissolved in tetrahydrofurane. Insolublematerial was filtered off. The filtrate was evaporated and the obtained material was purified by HPLC and preparative thin layer chromatography to give 13 mg of the title compound as solid material.
[000400] To a solution of Compound 24C (4.5 g, 33 mmol) in THF (20 mL) was added ft-BuLi (15 mL) at -78 C under N2 and the mixture was stirred for 30 min, before the addition of diethyl oxalate (10.8 g, 74 mmol). The mixture was stirred at -78 C for 1 h, and quenched with addition of aq sat. NH4C1. It was extracted with ethyl acetate (2 x 50 mL), washed with sat.NaHC03 (50 mL x 2), brine (50 mL), dried over Na2S04, concentrated, and purified by column chromatography on silica gel (ethyl acetate in petroleum ether, 20% v/v) to give Compound 24D (2.5 g, yield 32%) as a yellow solid.
With polyphosphoric acid; In toluene; at 90℃; for 3h;
[000399] A solution of polyphosphoric acid (90 g) in toluene was stirred to 90 C, then to the solution was added Compound 24B (15 g, 75 mmol) in toluene (20 mL) and the mixture was stirred at 90 C for 3 h, then poured into ice, and stirred for 30 min. It was extracted with ethyl acetate (100 mL x 2), washed with brine (100 mL x 1), dried over Na2S04, concentrated, and purified by column chromatography on silica gel (petroleum ether, 100% v/v) to yield Compound 24C (4.5 g, yield 44%) as a red liquid. 1H-NMR (CDC13, 400 MHz) major characteristic peaks: delta (ppm) 6.742-6.746 (m, 1H), 6.994-7.035 (m, 1H), 7.24- 7.26 (m, 1H), 7.41-7.44 (m, 1H), 7.651-7.655 (d, J= 1.6 Hz, 1H).
N-((1R,2R)-1-(2,3-dihydrobenzo[b][1,4]dioxin-6-yl)-1-hydroxy-3-(pyrrolidin-1-yl)propan-2-yl)-2,2-difluoro-2-(5-fluorobenzofuran-2-yl)acetamide[ No CAS ]
2-(bromodifluoromethyl)-5-fluorobenzofuran[ No CAS ]
Yield
Reaction Conditions
Operation in experiment
48%
With tert.-butylhydroperoxide; In decane; dichloromethane; acetonitrile; at 20℃; for 16h;
General procedure: To a solution of substrate 1 (1.0 mmol, 1 equiv), NaSO2CF2Br (23.4 mg, 2.0 mmol, 2.0 equiv) in CH2Cl2 (7.0 mL) and CH3CN (3.5 mL) at room temperature was slowly added TBHP (5.0-6.0 M in decane, 1.4 mL, 7 equiv). The reaction was then stirred for 16 h. After the reaction was complete, the reaction mixture was concentrated under vacuum and the crude product was purified by column chromatography on silica gel to give the product.
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