The pyrazole 3 was synthesized

February 23, 2024

• Title:       

  The pyrazole 3 was synthesized

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  4-Heterocyclylpiperidines as selective high-affinity ligands at the human dopamine D4 receptor

• Mark:

  Scheme 1

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  The pyrazole 3 was synthesized (Scheme 1) starting  from 3-quinuclidinone (38). Condensation with 4-chlorobenzaldehyde gave the unsaturated ketone 39, which  on treatment with hydrazine and base18 ring opened to  give pyrazole 4. Alkylation with 4-chlorobenzyl chloride  gave the lead compound 3. Other compounds in Table  2 were made by alkylation of pyrazole 4 with alkyl  halides, with the exception of the N-methylpiperidine  5, which was made by a reductive amination of pyrazole  4 with formaldehyde and sodium borohydride.