Patent EP1229031 (http://l2.espacenet.com/dips/viewer?PN=EP1229031&CY=gb&LG=en&DB=EPD)
A flat bottom separable flask with an internal volume of 500 mL as shown in fig 1 was charged with 50.0 g (0.409 mol) of 1,2 methylenedioxybenzene and 25 mL of 4-methyl-2-pentanone...in a nitrogen atmosphere, and the mixture was cooled to -5° with stirring.
Then a mixture of 83.4 g (0.450 mol) of a 40% by weight aqueous glycoxylic acid solution and 85.8 g (0.839 mol) of 96% by weight sulfuric acid was added dropwise thereto, and the mixture was stirred at -5° for 21 hours.
Thereafter, the reaction solution was neutralized by adding 102.0 g (1.67 mol) of 28% by weight aqueous ammonia little by little...
Preparation of piperonal.
Harada, Katsumasa; Aoi, Motojiro; Shirai,
Masashi; Furuya, Toshio. (Ube Industries, Japan).
CA 124:317136
Abstract
Piperonal (I), useful as an intermediate for pharmaceuticals and agrochems., is prepd. by oxidn. of 3,4-methylenedioxymandelic acid (II) by a nitrate or nitrite salt in the presence of sulfuric acid. Thus, a soln. of sodium nitrate 15.3 g in 16 mL water was added during 2 h to a mixt. of II 45.6 g and 97 wt.% sulfuric acid 55 g in toluene 75 mL at 50°; after the addn. of said soln. is completed and gas generation ceased, the reaction mixt. was stirred for a further 30 min to give, after workup, 96% I. The title method is highly
economical.
Method for producing piperonal.
CA 124:117294
Abstract
Piperonal (heliotropin) (I), which is a heliotrope fragrant base, widely used in cosmetic fragrants, and also useful a synthetic raw material for drugs and agrochems., and as a brightener for metal plating, is prepd. by oxidn. of 3,4-methylenedioxymandelic acid (II) with HNO3 in the presence of H2SO4. Thus, 15.8 g 61 wt.% HNO3 was added dropwise over 2 h to a stirred mixt. of H2O 123.4, 97 wt.% H2SO4 55, II 45.6 g, and 75 mL PhMe at 50-54° and the resulting
mixt. was allowed to react at 54° for 30 min, cooled to room temp., and extd. with toluene to give 96% I.
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