GB317381A - Improvements in and relating to the production of aromatic hydroxyaldehydes - Google Patents

Abstract

317,381. Graesser-Monsanto Chemical Works, Ltd., and Hudson, D. P. April 14. 1928. Vanillin; bourbonal.-Protocatechuic aldehyde is produced by oxidation of 3-alkoxymÞthoxy-4- hydroxy-1-propenylbenzene bv means of nitrobenzene or a nitrotoluene in the presence of alkali, the alkoxymethoxy group being hydrolyzed during the process. The product is isolated in the form of its bisulphite compound. A mixture of 3-alkoxymethoxy-4-hydroxy- and 4-alkoxymethoxy-3-hydroxy-1-propenylbenzenes mav be similarly oxidized, the unoxidized 4-alkoxymethoxy - 3 - hydroxy - 1 - propenylbenzene being worked up into isoeugenol or a homologue, by alkylation and hydrolysis. The isoeugenol etc. may be further converted into vanillin or a homologue thereof. According to examples, (1) 3- methoxy-4-hydroxy-1-propenylbenzene (methoxyisoeugenol) is oxidized by means of nitrobenzene in the presence of caustic potash, and a toluene solution of the resulting protocatechuic aldehyde is extracted with aqueous sodium bisulphite, and the bisulphite solution acidified to liberate the aldehyde, (2) safrole or isosafrole is treated with alcoholic potash under pressure to give a mixture of 3-ethoxymethoxy-4-hydroxy- and 4-ethoxymethoxy-3-hydroxy-1-propenylbenzenes, which is oxidized, possibly after purification, by means of nitrobenzene and aqueous potash; the reaction products are carefully acidified, and agitated with toluene, protocatechuic aldehyde is extracted from the toluene solution by means of bisulphite, and 4-ethoxymethoxy-3-hydroxy-1-propenylbenzene is then recovered' by evaporation; the 4- ethoxy-4-bydroxy-1-propenylbenzene is alkylated e.g., by means of dimethylsulphate-p-toluenesulphonic alkylester, or alkyl halides, and the resulting 4-alkoxymethoxy-3-alkoxy-1-propenylbenzene hydrolyzed to 3-alkoxy-4-hydroxy-1-propenylbenzene by means of dilute alcoholic hydrochloric acid; on oxidation with nitrobenzene and alkali, the corresponding aldehyde, e.g., vanillin or bourbonal, is obtained. Specification 285,451 is referred to.