| 91% |
|
In a 250 ml flask, equipped with coolant and magnetic stirring, the following were charged, under argon flow, in the order: <strong>[6964-21-2]3-thiopheneacetic acid</strong> (Aldrich) (0.711 g; 5 mmoles), palladium(II)acetate [Pd(OAc)2] (Aldrich) (0.023 g; 0.1 mmol), triphenylphosphine [PPh3] (Aldrich) (0.052 g; 0.2 mmol), potassium carbonate [K2CO3] (Aldrich) (1.382 g; 10 mmol), anhydrous N,N- dimethylformamide (DMF) (Aldrich) (30 ml) and 2-bromothiophene-3- carbaldehyde (Aldrich) (0.955 g; 5 mmoles): the reaction mixture was heated to 110C and kept at said temperature, under stirring, for 12 hours. Subsequently, the reaction mixture was cooled to room temperature (25C) and 9- (bromomethyl)nonadecane (Sunatech) (3.614 g; 10 mmol) was added: the reaction mixture was left, under stirring, at room temperature (25C), for 4 hours. Subsequently, the reaction mixture was placed in a 500 ml separating funnel, diluted with a 0.1 M ammonium chloride solution (NH4CI) (Aldrich) (3x 100 ml) and extracted with ethyl acetate (Aldrich) (3 x 100 ml), obtaining an aqueous phase and an organic phase. The entire organic phase (obtained by combining the organic phases deriving from the three extractions) was washed to neutral with water (3 x 50 ml) and subsequently anidrified on sodium sulphate (Aldrich) and evaporated. The residue obtained was purified by elution on a chromatographic column of silica gel [(eluent: n-heptane/ethyl acetate, 9/1, v/v) (Carlo Erba)], obtaining 2.342 g of 2-octyldodecyl-benzo[2,1-b;3,4- b’]dithiophene-4-carboxylate of formula (C) as straw yellow oil (yield 91%). |
| 61% |
|
2-Bromo-3-thiophenecarboxaldehyde (1.91 g, 10 mmol) was added to a solution of <strong>[6964-21-2]3-thiopheneacetic acid</strong> (1.42 g, 10 mmol), Pd(OAc)2 (224 mg, 0.1 mmol), PPh3 (524 mg, 0.2 mmol), and K2CO3 (2.76 g, 20 mmol) in anhyd DMF (50 mL) and the mixture was stirred to 110 C for 24 h. The reaction suspension was then cooled to 50 C and then 2-octyldodecyl bromide (3.61 g, 10 mmol) was added in one portion together with a catalytic amount of Bu4NI (184 mg, 0.5 mmol). The mixture was stirred for a further 24 h. After removal of solvent under reduced pressure, the crude mixture was purified by flash chromatography (SiO2; n-hexanes/EtOAc/CH2Cl2 (10:0.5:0.5). The pure product 6 was obtained as a colorless oil (61%), together with a small amount of 2-octyldodecyl-3-thiophene acetate (11%).6 Yield: 3.14 g (61%); Rf = 0.34 (99:0.5:0.5 hexanes/EtOAc/CH2Cl2). 1H NMR (CDCl3, 300 MHz): δ = 8.56 (s, 1H), 8.36 (d, J = 5.6 Hz, 1H), 7.53 (d, J = 5.6 Hz, 1H), 7.50 (d, J = 5.4 Hz, 1H), 7.44 (d, J = 5.4 Hz, 1H), 4.36 (d, J = 5.7 Hz, 2 H), 1.88 (m, 1H), 1.55-1.20 (m, 34 H), 0.87 (t, J = 7.0 Hz, 6 H). 13C NMR (CDCl3, 75 MHz): δ = 166.9, 137.8, 136.0, 135.6, 134.7, 125.7, 125.4, 125.2, 125.0, 124.2, 122.3, 67.8, 37.4, 31.8, 31.4, 29.9, 29.6, 29.5, 29.4, 29.2, 26.7, 22.6, 14.0. FIA-MS: m/z = 515 [M + 1]+, 1029 [2 M + 1]+. Anal. Calcd for C31H46O2S2: C, 72.32; H, 9.01. Found: C, 72.0; H, 8.8. |
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