96806-57-4

Upstream product

• 98369-56-3 (E)-4,5-di(benzyloxy)-2,β-dinitrostyrene 
• 108074-44-8 trans-3,4-dihydroxy-β-nitrostyrene 
• 73635-75-3 4,5-dihydroxy-2-nitrobenzaldehyde 
• 712-97-0 6-nitro-1,3-benzodioxole-5-carbaldehyde 
• 73635-74-2 5-(Chloromethoxy)-4-hydroxy-2-nitrobenzaldehyde 
• 139-85-5 3,4-dihydroxybenzaldehyde 
• 98369-55-2 (E)-4,5-dihydroxy-2,β-dinitrostyrene 

Downstream Products

• 3131-52-0 1H-indole-5,6-diol 
• 712-97-0 6-nitro-1,3-benzodioxole-5-carbaldehyde 

Relevant academic research and scientific papers

Expedient synthesis of 5,6-dihydroxyindole and derivatives via an improved Zn(II)-assisted 2,β-dinitrostyrene approach

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 the preparation of substituted indoles

A process for the preparation of 5,6-disubstituted indoles in which a 4-5-disubstituted-2,β-nitrostyrene is subjected to a reductive cyclization in the presence of a water soluble dithionite salt.

Process for preparing 5,6-dihydroxyindole

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.

SYNTHESIS OF 5,6-DIHYDROXYINDOLE: A NOVEL REDUCTIVE CYCLIZATION OF (E)-4,5-DIHYDROXY-2,β-DINITROSTYRENE

A unique catalytic reductive cyclization of (E)-4,5-dihydroxy-2,β-dinitrostyrene (1) to 5,6-dihydroxyindole (2) is reported.Compound 1 is obtained either by one-step CF3CO2H deprotection of 4,5-dibenzyloxy-2,β-dinitristyrene (7), or by an improved two-step demethylenation of 6-nitropiperonal (5), followed by condensation with CH3NO2.