PROCESSES FOR THE PREPARATION OF ROXADUSTAT AND INTERMEDIATES THEREOF

The present invention provides new procedure and intermediates for the preparation of Roxadustat (1) comprising: (A) reducing a compound of formula 3′, 3″ or a mixture thereof: (3′), (3″) wherein Pg is H or a OH protecting group, Ri is alkyl, aryl, or arylalkyl; R2, R3, R4, and Rs each independently represents alkyl, arylalkyl or alkenyl, or R2 and R3 and/or R4 and Rs, taken together with the nitrogen atom to which they are bonded, each independently form a ring selected from: (I), wherein R6 is H or CI-6 alkyl; R7 is Ci to C6 alkyl and X- is an anion selected from the group consisting of halide, O-SO4-R7 wherein R7 is Ci to C6 alkyl, or O-SO2-Rs wherein Rs is phenyl, tolyl, methyl or trifluoromethyl; to form a compound of formula (2′) wherein Pg is H or an OH protecting group, Ri is alkyl, aryl, or arylalkyl; and removing the Ri group and where present removing the OH protecting group; or (B) reducing a compound of formula 4′, a compound of formula 4″ or a mixture thereof: (4′), (4″) wherein Pg is H or an OH protecting group; Ri is H, alkyl, aryl, or arylalkyl; R2, R3, R4, and R5 each independently represents alkyl, aryl, arylalkyl or alkenyl; or R2 is Ci-4 alkyl and R3 is Ci-4 alkoxy; or R2 and R3 and/or R4 and R5, taken together with the nitrogen atom to which they are bonded, each independently form a group selected from: (I) wherein R6 is H or CI-6 alkyl; and where Ri is not H, removing the Ri group, and, where present removing the OH protecting group.