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Pyrazoles by dealkylation of pyrazolium salts
Author(s) -
Cross Barrington,
Arotin Robert L.,
Ruopp Charles F.
Publication year - 1980
Publication title -
journal of heterocyclic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.321
H-Index - 59
eISSN - 1943-5193
pISSN - 0022-152X
DOI - 10.1002/jhet.5570170512
Subject(s) - chemistry , piperidine , alkylation , demethylation , methyl iodide , iodide , ethanol , organic chemistry , medicinal chemistry , catalysis , biochemistry , gene expression , gene , dna methylation
A rapid, convenient conversion of 1,2‐dimethylpyrazolium salts ( 1 ) to 1‐methylpyrazoles ( 2 ) is accomplished in piperidine or 3‐methylpiperidine at temperatures ≥ 106°. This demethylation represents a particularly useful procedure for the synthesis of 3‐ and 5‐substituted aminopyrazoles, which are not readily obtainable by other methods. The 50:50 mixture of piperidinopyrazole isomers 2b can be obtained directly by treating 3‐chloro‐1,2‐dimethyl‐5‐phenylpyrazolium iodide (3b ) with piperidine in ethanol at 106°.