METHOD FOR THE SYNTHESIS OF RHEIN AND DERIVATIVES THEREOF

摘要

The invention relates to a method for the synthesis of a compound of the formula (1) in which R<SUB>1</SUB> is a hydroxyl or acetoxy group, characterised it comprises: a metallation step of the aromatic cycle of a compound of the formula (2) in which R<SUB>2</SUB> and R<SUB>3</SUB> independently represent a C<SUB>1</SUB> - C<SUB>4</SUB> alkyl group selectively in the ortho position of the -OR<SUB>2</SUB> substituent; reacting the metalled compound thus obtained with a compound of the formula (3) in which R<SUB>2</SUB> is such as defined above and R<SUB>4</SUB> is an electrophile group selected from the group including the following groups -CHO, -COX with X=Cl, Br, I, -COCN, -CONCH<SUB>3</SUB>OCH<SUB>3</SUB>, -CON(R)<SUB>2</SUB>, -COOR or R is a C<SUB>1</SUB> - C<SUB>4</SUB> alkyl group and is preferably a -CHO or -COCl group; followed by the steps of acid hydrolysis, reduction, cycling and oxidation in order to obtain the compound (1).