Issue 21, 2022

Base-mediated [3 + 2]-cycloannulation strategy for the synthesis of pyrazolo[1,5-a]pyridine derivatives using (E)-β-iodovinyl sulfones

Abstract

Pyrazolo[1,5-a]pyridines continue to occupy a special place in medicinal chemistry, but the direct construction of 3-sulfonyl analogues remains unexplored. Under basic conditions, pyridinium-N-amine and the corresponding dipolar aminide played a vibrant role in [3 + 2]-cycloaddition using (E)-β-iodovinyl sulfones. K2CO3-mediated tandem cycloannulative-desulfonylation of (E)-β-iodovinyl sulfones with 1-aminopyridinium iodide is realized to access 2-substituted pyrazolo[1,5-a]pyridines in good to high yields. An essential modification of the dipolar N-tosylpyridinium imide allows the first preparative synthesis of 3-sulfonyl-pyrazolo[1,5-a]pyridines in moderate to high yields. Of note, the metal-free protocol features a broad substrate scope with good functional group tolerance and compatibility. The efficacy of the process was proved with gram-scale reactions, and a plausible mechanism is also presented based on concrete results.

Graphical abstract: Base-mediated [3 + 2]-cycloannulation strategy for the synthesis of pyrazolo[1,5-a]pyridine derivatives using (E)-β-iodovinyl sulfones

Supplementary files

Article information

Article type
Paper
Submitted
15 Mar 2022
Accepted
13 Apr 2022
First published
13 Apr 2022

Org. Biomol. Chem., 2022,20, 4331-4337

Base-mediated [3 + 2]-cycloannulation strategy for the synthesis of pyrazolo[1,5-a]pyridine derivatives using (E)-β-iodovinyl sulfones

R. Jannapu Reddy, N. Sharadha and A. Haritha Kumari, Org. Biomol. Chem., 2022, 20, 4331 DOI: 10.1039/D2OB00499B

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