<p>Leuco-quinizarin, characterized by its highly active diketone skeleton, is a versatile reactant that can function as both an electrophile and a nucleophile. We demonstrate that Pt-Ni bimetallic nanoparticle catalysts, immobilized on a composite support of dimethylpolysilane (DMPSi) and Al₂O₃ (M/DMPSi-Al₂O₃), exhibit both high activity and selectivity in the hydrogenation of quinizarin to leuco-quinizarin. This study investigates the influence of the Ni/Pt ratio in Pt-Ni/DMPSi-Al₂O₃ catalysts on their structure and catalytic activity. A higher Ni/Pt ratio resulted in improved catalytic performance for the selective hydrogenation of quinizarin to leuco-quinizarin in both batch and continuous-flow systems. We also developed a comprehensive continuous-flow synthetic process that integrates the continuous-flow hydrogenation of quinizarin to leuco-quinizarin catalyzed by Pt-Ni/DMPSi-Al₂O₃ with the derivatization reaction of leuco-quinizarin (Marschalk reaction).</p>