A method for preparing a composition comprising a compound of formula: wherein R 1, R 2, R 3, R 4, R 5, and R 6 are each H; X 1 is -N(R 8)(R 9), wherein R 8 and R 9 are C 1 -C 6 alkyl; Ar is wherein R 11, R 12, R 14, and R 15 are H and R 13 is pyrrolidinylcarbonyl, and a palladium contaminant, the method comprising: (a) contacting a compound of formula (Ia): wherein R 1, R 2, R 3, R 4, R 5, R 6, and X 1 are as defined as formula; X 2 is an amine protecting group; and Y is a halo group, with Ar-B(OR 10) 2, wherein Ar is as defined for formula and R 10 is H, in the presence of a palladium catalyst to provide a crude composition comprising a solvent comprising ethanol and less than about 0.5% water and one or more palladium contaminants; (b) clarifying the crude composition by filtration through diatomaceous earth; (c) adding a palladium scavenger to the crude composition for a predetermined time, wherein the palladium scavenger is selected from functionalized silica particles and activated carbon particles, wherein the functionalized silica particles comprise a functional group selected from aminopropyl and mercaptopropyl, and wherein the activated carbon comprises porous, spherical, non-functional carbon particles with a surface area of about 1200 m 2 /g, an average pore diameter of about 1 nm, and a particle diameter of about 0.3 mm to about 0.8 mm; and (d) removing the palladium scavenger to yield a purified composition comprising the compound of formula and a palladium contaminant, wherein the palladium contaminant in the purified composition is present in a concentration of less than 50 ppm by ICP-OES. R 1, R 2, R 3, R 4, R 5, and R 6 are each H; X 1 is -N(R 8)(R 9), wherein R 8 and R 9 are C 1 -C 6 alkyl; Ar is wherein R 11, R 12, R 14, and R 15 are H and R 13 is pyrrolidinylcarbonyl, (a) contacting a compound of formula (Ia): wherein R 1, R 2, R 3, R 4, R 5, R 6, and X 1 are as defined as formula; X 2 is an amine protecting group; and Y is a halo group, with Ar-B(OR 10) 2, wherein Ar is as defined for formula and R 10 is H, in the presence of a palladium catalyst to provide a crude composition comprising a solvent comprising ethanol and less than about 0.5% water and one or more palladium contaminants; R 1, R 2, R 3, R 4, R 5, R 6, and X 1 are as defined as formula; X 2 is an amine protecting group; and Y is a halo group, (b) clarifying the crude composition by filtration through diatomaceous earth; (c) adding a palladium scavenger to the crude composition for a predetermined time, wherein the palladium scavenger is selected from functionalized silica particles and activated carbon particles, wherein the functionalized silica particles comprise a functional group selected from aminopropyl and mercaptopropyl, and wherein the activated carbon comprises porous, spherical, non-functional carbon particles with a surface area of about 1200 m 2 /g, an average pore diameter of about 1 nm, and a particle diameter of about 0.3 mm to about 0.8 mm; and (d) removing the palladium scavenger to yield a purified composition comprising the compound of formula and a palladium contaminant, wherein the palladium contaminant in the purified composition is present in a concentration of less than 50 ppm by ICP-OES.