Compound RC-11

Synthetic procedure: See article for the definitive version of this procedure and for full experimental details.

In argon, potassium tert-butoxide (0.903 g, 8.03 mmol) dissolved in 3 mL of THF was added to a THF solution (4 mL) of methyltriphosphonium bromide (2.60 g, 7.30 mmol) in an ice bath. After stirring at room temperature for 100 min, 4-(N,N-diphenylamino)benzaldehyde (1.995 g, 7.30 mmol) was added and stirred overnight. Crude ¹H-NMR showed that only 10% of the precursor starting materials were reacted. The mixture was evacuated to dryness at 90 °C for 4 h and then transferred to a nitrogen glove box. THF was added to the mixture and cooled to -30 °C. Under stirring, 1.6 M n-butyllithium (3.50 mL, 5.6 mmol) was added. After 30 min, the mixture still showed unreacted methyltriphosphonium bromide via ¹H NMR. 1.6 M n-butyllithium (0.90 mL, 1.44 mmol) was added and the mixture turned dark yellow. A THF solution of methyltriphosphonium bromide (1.80 g, 6.59 mmol, pre-dried under vacuum at 90 °C for 4 h) and n-butyllithium (4.10 mL, 6.56 mmol) was added, and the mixture turned dark green. After 9 h, the reaction was transferred out of the glove box, quenched with water and extracted with dichloromethane three times. The organic layer was collected, dried on magnesium sulfate, and filtered, and then the solvent was evaporated. The crude product dissolved in dichloromethane was filtered through a silica plug using petroleum ether as eluent. The light yellow portion that came out first was collected and again filtered through a silica plug. The dark yellow portion that moved slowly was discarded. The solvent was evaporated to yield N,N-diphenyl-4-vinylaniline. Yield: 0.75 g (2.77 mmol, 38%). ¹H NMR (299.82 MHz, CDCl₃) 6.97 – 7.33 (m, 14 H), 6.66 (dd, J = 17.6, 10.9 Hz, 1H), 5.64 (dd, J = 17.6, 1.0 Hz, 1H), 5.15 (dd, J = 10.9, 1.0 Hz, 1H).

N,N-diphenyl-4-vinylaniline (0.700 g, 2.58 mmol), 3,5-dibromobenzaldehyde (0.306 g, 1.16 mmol), palladium acetate (15 mg, 0.067 mmol), potassium carbonate (0.320 g, 2.32 mmol), tetra-n-butylammonium bromide (0.374 g, 1.16 mmol), and dimethylformamide (5 mL) were mixed in a Schlenk flask and sparged with argon for 30 min under stirring. Under a blanket of argon, the reaction was heated to 90 °C for 10 h. After cooling to room temperature, dichloromethane (50 mL) was added, and the mixture was extracted with an aqueous solution of HCl three times (1.0 M, 100 mL in total). The organic layer was collected and the solvent was evaporated. This crude product was dissolved in a small amount of dichloromethane and hexanes was added. The bottom layer of brown solution was discarded, and the top layer of cloudy light yellow solution was collected and evacuated to induce precipitation. The cloudy light yellow supernatant contained the product and was collected. The precipitate also contained the product and impurities and so was again purified following the same procedures until the color of the precipitate changed from light brown to dark brown. The supernatants were combined and dried under vacuum yielding 3,5-bis(4-(diphenylamino)styryl)benzaldehyde as a yellow solid. Yield: 0.514 g (0.798 mmol, 62%). ¹H NMR (299.82 MHz, acetone-d₆): δ 10.09 (s, 1H), 8.11 (s, 1H), 7.99 (s, 2H), 7.58 (d, J = 8.6 Hz, 4H), 7.44 (d, J = 16.4 Hz, 2H), 7.37 – 7.24 (m, 10H), 7.06 – 7.14 (m, 12 H), 7.03 (d, J = 8.7 Hz, 4H).

To a Schlenk flask, acetonitrile (6.5 mL), chloroform (6.5 mL) and anhydrous magnesium sulfate (1.05 g) were added and the mixture was sparged with argon for 30 min. After addition of 3,5-bis(4-(diphenylamino)styryl)benzaldehyde (0.333 g, 0.517 mmol), cyanoacetic acid (0.072 g, 0.941 mmol), and piperidine (0.05 mL, 0.51 mmol), the mixture was heated to 80 °C for 12 h and then cooled to room temperature. The reaction mixture was filtered and the solvent of the filtrate was evaporated. The crude product was dissolved in dichloromethane and filtered through a silica plug using hexanes:ethyl acetate (8:1, v/v) as eluent to flush out the byproducts. The product which remained on the silica plug was flushed out with dichloromethane, methanol, and then dichloromethane:methanol (1:1, v/v). The solvent was evaporated and the solid was rinsed with methanol and evacuated to dryness as a dark yellow solid. Yield: 0.300 g (0.422 mmol, 82%). ¹H NMR (499.18 MHz, DMSO-d₆) δ 7.96 (s, 1H), 7.90 (s, 2H), 7.87 (s, 1H), 7.53 (d, J = 8.6 Hz, 4H), 7.37 – 7.24 (m, 10H), 7.14 (d, J = 16.3 Hz, 2H), 7.10 – 7.01 (m, 12H), 6.97 (d, J = 8.7 Hz, 4H). ESI-MS (TOF): m/z 711.21 ([M]⁺), calculated 711.29.

PubChemID:

347915350

MDL Molfile:

41557_2018_BFnchem2892_MOESM4_ESM.mol

ChemDraw:

41557_2018_BFnchem2892_MOESM5_ESM.cdx