[N+:1]([C:4]1[CH:9]=[CH:8][C:7]([Cl:10])=[CH:6][C:5]=1[N:11]=[N:12][C:13]1[CH:18]=[C:17]([CH3:19])[CH:16]=[C:15]([C:20]([CH3:23])([CH3:22])[CH3:21])[C:14]=1[OH:24])([O-])=O.C(N)CCC.[H][H]>[Pt].C1(C)C(C)=CC=CC=1>[Cl:10][C:7]1[CH:8]=[CH:9][C:4]2=[N:1][N:12]([C:13]3[CH:18]=[C:17]([CH3:19])[CH:16]=[C:15]([C:20]([CH3:23])([CH3:22])[CH3:21])[C:14]=3[OH:24])[N:11]=[C:5]2[CH:6]=160 g of 2-nitro-5-chloro-2'-hydroxy-3'-tert-butyl-5'-methylazobenzene (purity 86%), 40 g of xylene, 60 g of n-butylamine and 1 g of 1% Pt on activated carbon are put into a 300 ml hydrogenation reactor at room temperature under argon. Argon is then replaced by hydrogen. After the injection of 10 bar hydrogen, the hydrogenation is carried out at 35°-37° C. with intensive stirring. The heat released is removed by cooling. The end of the hydrogenation reaction is easily detectable by the hydrogen absorption ceasing after 2 mol equivalents of hydrogen, relative to the azobenzene starting product. The total hydrogenation time is about 1.5 hours.
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