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1 Wiadomości Chemiczne

1 1999

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Metody syntezy witaminy K3

Kowalski Jan, Płoszyńska Jolanta, Sobkowiak Andrzej

Wiadomości Chemiczne

1999

[Z] 53, 5-6

401-413

The preparation of 2-methyl-1,4naphthoquinone (menadione) is a challenging problem in catalysis research. This reaction is the key step in the synthesis of vitamin K and its derivatives. The preparation of naphthoquinones usually requires the direct oxidation of arenes by stoichiometric quantities of chromic acid/sulfuric acid. The reaction can be also achieved by the use of Ce(IV) compounds and other transition metal compounds as oxidants and with hydrogen peroxide. The other approach is to use Diels-Alder reaction between 1,3-butadiene and p-benzoquinone with the subsequent oxidation of the adduct formed . The indirect electrolysis with ruthenium compounds and dichromate as mediators were also applied in the process. In the previous work we reported that the electrochemical oxidation of 2-methylnaphthalene in glacial acetic acid gives monoacetates, mainly 2-methylnaphthalene-1-acetate, but 2-methylnaphthalene-1,4-diacetate and 2-methyl-1,4-naphthoquinone were also formed. This prompted us to investigate the electrochemical behavior of 2-methylnaphthalene-1,4diacetate. It is shown that the electrochemical oxidation of the compounds in glacial acetic acid yields 2-methyl-1,4naphthoquinone as a sole product. The process is irreversible and diffusion controlled. The material and current yields of the process are 94 and 99% respectively.