96806-57-4Relevant articles and documents
Expedient synthesis of 5,6-dihydroxyindole and derivatives via an improved Zn(II)-assisted 2,β-dinitrostyrene approach
Novellino, Luisa,D'Ischia, Marco,Prota, Giuseppe
, p. 793 - 796 (1999)
A facile 3-step synthesis of 5,6-dihydroxyindole (4a) is reported, featuring the Zn(II)-controlled regioselective nitration of 3,4- dihydroxynitrostyrene (2) with tetranitromethane at pH 8.0, and the reductive cyclization of the resulting 4,5-dihydroxy-2,β-dinitrostyrene (3a) with Na2S2O4/Zn(II) at pH 4. The latter procedure was successfully extended to the conversion of the 2,β-dinitrostyrenes 3b and 3c to 5,6-dibenzyloxyindole (4b) and 5,6-diacetoxyindole (4c) in good-to-high yields.
Process for preparing 5,6-dihydroxyindole
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, (2008/06/13)
5,6-Dihydroxyindole is prepared by the catalytic reductive cyclization of 4,5-dihydroxy-2,β-dinitrostyrene in a single step using hydrogen with a palladium, platinum or rhodium catalyst in a polar hydroxylic reaction system. No reaction byproducts or only a single reaction byproduct are produced. The 4,5-dihydroxy-2,β-dinitrostyrene intermediate can be prepared by the chemoselective debenzylation of 4,5-dibenzyloxy-2,β-dinitrostyrene using trifluoroacetic acid. 5,6-Dihydroxyindole is a useful component in hair dye formulations and as an intermediate in the synthesis of melanin.
