Crystal structure of 2,5-bis(2,5-dimethoxybenzyl)- 3,6-dimethyl-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione, C 26 H 28 N 2 O 6

C 26 H 28 N 2 O 6 , monoclinic, P 2 1 / c (no. 14), a = 15.962(9) Å, b = 14.828(8) Å, c = 9.929(5) Å, β = 93.303 ° , V = 2346(2) Å 3 , Z = 4, R gt ( F ) = 0.0515, w R ref ( F 2 ) = 0.1621, T = 296(2) K.


Source of material
A dichloromethane (12 mL) solution of (2,5-dimethoxyphenyl) methanamine (1.0 g, 6 mmol) and triethylamine (0.03 mL, 8 mmol) was added to a 50 ml round bottom flask and cooled to 0 °C.At this temperature, fumaric chloride (0.7 ml, 4 mmol) in dichloromethane (6 mL) was added drop by drop within 1 h, and white smoke was observed, and a large amount of white precipitation was observed in the reaction mixture.After removing the ice bath, reaction mixture was stirred at room temperature overnight.After the reaction was completed, the solution was filtered first, and the obtained  8.284 g, 20 mmol) and isopropyl acetate (150 mL) were added to a 500 mL round bottom flask.Then a dimethylformamide solution of p-toluenesulfonic acid (20 mL, 0.10 mol/L) was added, and the reaction mixture was heated at 105 °C (oil bath) in a nitrogen atmosphere, stirring for 12 h.It was observed that the white solid gradually dissolved, and the solution turned brown and yellow.After the reaction, it was cooled to room temperature, and the reaction mixture was concentrated under reduced pressure to remove most of the solution.The residue was dissolved in ethyl acetate (300 mL) and washed by 5 % HCl aqueous solution (200 mL) twice, saturated NaHCO 3 solution (200 mL) and water.The organic phase was separated, dried with anhydrous sodium sulfate, and concentrated under reduced pressure to remove the solvent.The crude product was purified by silica gel column chromatography (dichloromethane/ethyl acetate 10:1) and vacuum dried to afford N 1 ,N 4 -diacetyl-N 1 ,N 4 bis(2,5-dimethoxybenzyl)fumaramide (7.47 g, 15 mmol).N 1 ,N 4 -diacetyl-N1,N4-bis(2,5-dimethoxybenzyl)fumaramide (2.8 g, 5.63 mmol), acetonitrile (50 mL), PPh 3 (1.495g, 5.7 mmol) and pyridinium p-toluene sulfonate (0.7288 g, 2.9 mmol) were added to a 100 mL round bottom flask.The reaction mixture was stirred at 100 °C (oil bath) for 10 h.After the reaction, it was cooled to room temperature, and the yellow solid was separated.The reaction mixture was concentrated under reduced pressure to remove the acetonitrile solvent.The residual solid was dissolved in dichloromethane (200 mL) and extracted with water (200 mL).The organic phase was separated, dried with anhydrous sodium sulfate, filtered, and concentrated.The crude product was purified by silica gel column chromatography (dichloromethane/ethyl acetate = 8:1) to produce 2,5-bis(2,5-dimethoxybenzyl)-3,6-dimethyl-2,5-di-

Experimental details
Hydrogen atoms were placed in their geometrically idealized positions and constrained to ride on their parent atoms.

Table  :
Data collection and handling.

Table  :
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å  ).

Table  :
(continued) Crystals of the title compound were obtained by slow vaporization of a solution in CH 2 Cl 2 within one week.