Method for the preparation of pyridine-2,3-dicarboxylic acids

Claim 1

A method for the preparation of unsubstituted and substituted pyridine-2,3-dicarboxylic acids of formula I ##STR5## wherein R 1 , R 2 and R 3 are each hydrogen, C 1 -C 6 alkyl, hydroxy-C 1 -C 6 alkyl, C 1 -C 6 alkoxy, phenoxy, C 1 -C 4 haloalkyl, nitro, hydroxy, amino, C 1 -C 4 alkylamino, diloweralkylamino or C 1 -C 4 alkylamino, diloweralkylamino or C 1 -C 4 alkylsulfonyl group, carboxy, acyl, amido; or phenyl optionally substituted with one C 1 -C 1 alkyl, C 1 -C 4 alkoxy or halogen; difluoromethoxy, trifluoromethoxy, 1,1,2,2-tetrafluoroethoxy, C 3 -C 8 straight or branched alkenyloxy optionally substituted with one to three halogens, or C 3 -C 8 straight or branched alkynyloxy optionally substituted with one to three halogens; and when taken together, R 2 and R 3 may form a ring which may optionally be substituted, in which R 2 R 3 are represented by --(CH 2 ) 2 --Q-- or --(CH) 2 --Q--, wherein Q is oxygen, sulfur, or nitrogen, with the proviso that R 1 is hydrogen; comprising oxidizing a substituted quinoline of formula II ##STR6## wherein R 1 , R 3 and R 3 are as described in formula I above; X 1 , X 2 , X 3 , X 4 are each hydroxy, hydrogen, SO 3 H, SO 2 Cl, SH, Cl, F, Br, I, CO 2 H, NO 2 , or NR 2 , CONR 2 or COR wherein R is C 1 -C 4 alkyl or hydrogen; with the proviso that one of X 1 , X 2 , X 3 or X 4 is other than hydrogen; or the N-oxide thereof; or an acid addition salt thereof; in aqueous base with hydrogen peroxide.

Claim 2

A method for the preparation of unsubstituted and substituted pyridine-2,3-dicarboxylic acids of formula I ##STR5## wherein R 1 , R 2 and R 3 are each hydrogen, C 1 -C 6 alkyl, hydroxy-C 1 -C 6 alkyl, C 1 -C 6 alkoxy, phenoxy, C 1 -C 4 haloalkyl, nitro, hydroxy, amino, C 1 -C 4 alkylamino, diloweralkylamino or C 1 -C 4 alkylamino, diloweralkylamino or C 1 -C 4 alkylsulfonyl group, carboxy, acyl, amido; or phenyl optionally substituted with one C 1 -C 1 alkyl, C 1 -C 4 alkoxy or halogen; difluoromethoxy, trifluoromethoxy, 1,1,2,2-tetrafluoroethoxy, C 3 -C 8 straight or branched alkenyloxy optionally substituted with one to three halogens, or C 3 -C 8 straight or branched alkynyloxy optionally substituted with one to three halogens; and when taken together, R 2 and R 3 may form a ring which may optionally be substituted, in which R 2 R 3 are represented by --(CH 2 ) 2 --Q-- or --(CH) 2 --Q--, wherein Q is oxygen, sulfur, or nitrogen, with the proviso that R 1 is hydrogen; comprising oxidizing a substituted quinoline of formula II ##STR6## wherein R 1 , R 3 and R 3 are as described in formula I above; X 1 , X 2 , X 3 , X 4 are each hydroxy, hydrogen, SO 3 H, SO 2 Cl, SH, Cl, F, Br, I, CO 2 H, NO 2 , or NR 2 , CONR 2 or COR wherein R is C 1 -C 4 alkyl or hydrogen; with the proviso that one of X 1 , X 2 , X 3 or X 4 is other than hydrogen; or the N-oxide thereof; or an acid addition salt thereof; in aqueous base with hydrogen peroxide.