Croweacic acid derivatives -
Patent US3000902
Example 1 - 2-methoxy-3,4-methylenedioxybenzaldehyde (II) and 4-methoxy-2,3-methylenedioxybenzaldehyde (X): 25 g of ice-cold dimethyl formamide (DMF) was stirred while being treated dropwise with 50 g of phosphorus oxychloride. When the addition was complete, the mixture was allowed to warm to room temperature over a period of 30 minutes. 24 g of 1-methoxy-2,3-methylenedioxybenzene (I) was added and the mixture was stirred and heated at 100°C for 2 h. The reaction mixture was cooled, poured onto 400 g of ice and after 15-30 minutes extracted with four 100 mL portions of chloroform. Concentration of the combined chloroform extracts gave a 24 g residue of solids. The residue in 100 mL of benzene was put on a 9 inch long column containing 800 g of acid washed alumina and the product was eluted with 12 L of benzene in 80 fractions. Elution was continued with 6 L of chloroform in 50 additional fractions. Radial paper-gramss of selected fractions, using the system water:n-BuOH (200:1) showed UV fluorescent zones of Rf 0.73 +/- 0.03. The fluorescent zones from fractions 3-10 were of a dull gray -blue color, those from fractions 40 to 130 were of a light blue color, while those from fractions 11-39 were intermediate in color. All the zones gave positive reactions when sprayed with 2,4-dinitrophenylhydrazine reagent. On the basis of the differing fluorescent colors, fractions 3-10 were combined and 4.6 g of 2-methoxy-3,4-methylenedioxybenzaldehyde (II), mp 97-105°C was obtained. Recrystallization of the product from EtOH gave the purified aldehyde (II), mp 103-105°C. Fractions 40-130 were obtained and 10.7 g crude aldehyde (X) was obtained. Recrystallization of this product from 100 mL of EtOH yielded 2.7 g of 4-methoxy-2,3-methylenedioxybenzaldehyde (X), mp 85-86°C. Combinations of fractions 11-39 gave 4.8 g of a mixture of aldehydes (II) and (X).
