抄録
Catalytic reduction of 4, 4'-azopyridine 1, 1'-dioxide (I) in methanol with Raney nickel catalyst at atmospheric temperature and pressure results in formation of 4, 4'-hydrazopyridine (IV) via 4, 4'-azopyridine (V). The same reduction with palladium-carbon as a catalyst affords 4, 4'-hydrazopyridine 1, 1'-dioxide (VI) and the reduction stops at this stage. This shows that the reduction of N-oxide group precedes that of azo to hydrazo group when using Raney nickel as a catalyst, but reduction of the azo to hydrazo group alone takes place when palladium-carbon is used as a catalyst. In the case of 4, 4'-azoxypyridine 1, 1'-dioxide (II), the use of Raney nickel as a catalyst effects reduction of (II) to (IV) through (I) and (V), while the use of palladium-carbon produces (VI) through (I). In this case, reduction of azoxy to azo group is the first step and the rest is the same as in the case of (I). In the case of 2-styrylpyridine 1-oxide (III), reduction of N-oxide group precedes that of the double bond and 2-phenethylpyridine (VII) is formed via 2-styrylpyridine (VIII). When palladium-carbon is used as the catalyst, reduction of the double bond is said to precede that of N-oxide group and (VII) is formed via 2-phenethylpyridine 1-oxide (IX). This is in contrast to the use of Raney nickel as a catalyst.
