Trifluperidol, 4-[4-(α,α,α-trifluoro-m-tolyl)-4-hydroxypiperidino]-4′- fluorobutirophenone (6.3.3), is synthesized by reacting 1-benzyl-4-piperidone (3.1.48) with a Grignard reagent prepared from 1-trifluoromethyl-3-bromobenzene and magnesium that forms 1-benzyl-4-hydroxy-4-(3-trifluoromethylphenyl)piperidine (6.3.1), the reduction of which with hydrogen in the presence of a palladium on carbon catalyst removes the benzyl protecting group giving 4-hydroxy-4-(3-trifluoromethylphenyl)piperidine (6.3.2). Alkylation of the nitrogen atom of the last by ω–chloro-4-fluorobutyrophenone gives trifluperidol (6.3.3).
The 4'-chloro-4-fluorobutirophenone (6.3.4) needed for this is synthesized by the acylation of fluorobenzene using 4-chlorobutyric acid chloride.