4-Hydroxypyridine derivative + 1-Hydroxy-2-unsubstituted aromatic > 3,4-Dihydroxypyridine derivative + 1,2-Dihydroxyaromatic
[H][c:1]1[c:8][#6,#7;a:7][c:6][c:5][c:4]1-[#8;!$([O;H1]c1cccc([O;H1])c1):9][H]>>[#8:9]([H])-[c:4]1[c:5][c:6][#6,#7;a:7][c:8][c:1]1-[#8]([H])
[H][c:1]1[c:8][#6,#7;a:7][c:6][c:5][c:4]1-[#8;!$([O;H1]c1cccc([O;H1])c1):9][H]
[$([O;H1]c(:c):c([O;H1]):[c,n]),$([#7;H2]-c(:c):c([O;H1]):c),$(O[C;H2][C;H2]c1ccccc1)]
[#8:9]([H])-[c:4]1[c:5][c:6][#6,#7;a:7][c:8][c:1]1-[#8]([H])
[$(OC1=[C;R1]C2=C([C;R1]=C1O)[C,N]=CC=C2),$(Oc1cccc(c1O)[N+]([O-])=O)]
