Yield:-

Reaction Conditions:

with selenium(IV) oxide in pyridine at 117; for 6 h;Heating / reflux;

Steps:

15 2-(2',4'-dichlorophenyl)-3-nitro-4-carboxy pyridine (D2)

A mixture of 2-(2',4'-dichlorophenyl)-3-nitro-4-methyl pyridine (2.5 g, 8.82 mmole) and SeO2 (0.97, 8.82 mmole) in pyridine is heated at 117° C. for 6 h. The reaction is cooled to r.t., filtered and the solvent is evaporated under high vacuum. Compound D2 is used directly in the next step.

References:

US6352990,2002,B1 Location in patent:Page column 40