Abstract
Three synthetic methods for the preparation of 1,5-disubstituted 1,5,6,7-tetrahydro-4H-pyrazolo[4,3-c]pyridin-4-ones as heterocyclic histamine analogues were developed. The first method starts from easily available methyl 5-(2-aminoethyl)-1H-pyrazole-4-carboxylates, which were N-alkylated and the resulting secondary amines were cyclised in the presence of a base to give the title compounds in 17-92% yields (method A). Alternatively, the amines were first cyclised to the 5-unsubstituted pyrazolo[4,3-c]pyridin-4-ones. Subsequent N-benzylation afforded three of the title compounds in 36-49% yields (method B). The third method comprises a six-step transformation of methyl acrylate into 1-benzylpiperidine-2,4-dione. Treatment of the latter with N,N-dimethylformamide dimethylacetal (DMFDMA) followed by acid-catalysed cyclisation of the formed enaminone with methyl-, phenyl- and tert-butylhydrazine afforded the same three title compounds in 79-87% yields (method C).
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
