Characterization of the trimethyl silyl derivatives of 6-Amino-3-methyl-1,4-diphenyl-1,4-dihydropyrano[2,3-c]pyrazole-5-carbonitrile and its analogs by electron ionization gas chromatography/mass spectrometry

Published

June 27, 2025

Author(s)

Quan-Long Pu, Yufang Zheng, Edward P. Erisman

Abstract

Pyranopyrazoles have broad applications as pharmaceutical ingredients and biodegradable agrochemicals. The most extensively investigated are the pyrano[2,3 c]pyrazoles, with new synthetic products continually emerging. Gas chromatography/mass spectrometry (GC/MS) has difficulty in obtaining useful mass spectra under typical measurement conditions due to thermal degradation. However, analyzing trimethylsilyl (TMS) derivatives of 6-amino-3-methyl-1,4-diphenyl-1,4-dihydropyrano[2,3 c]pyrazole-5-carbonitrile and analogs provided characteristic ions by which the mass spectra fragmentation pathways could be determined. The fragmentation mechanism was shown to begin with a TMS radical transfer from the N to O and two α cleavage reactions with the loss of a C3HN2 radical to form a stable characteristic cation [M-65]+. The mass spectra of position isomers (o , m , and p ) of the substituent (Cl, Br, F, CH3, OCH3) on the 4 phenyl group were compared revealing that the ortho compound has a unique fragment ion peak m/z 261. Lastly, two isomeric di-TMS derivatives were observed the have fragmentation pathways and characteristic ions similar to mono-TMS derivatives.

Citation

Journal of Mass Spectrometry

Volume

60

Issue

7

Pub Type

Journals

Download Paper

https://doi.org/10.1002/jms.5150

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Keywords

fragmentation pathway, heterocycle, ortho-effect, pyrano[2, 3-c]pyrazole, retro Diels-Alder reaction

Citation

Pu, Q. , Zheng, Y. and Erisman, E. (2025), Characterization of the trimethyl silyl derivatives of 6-Amino-3-methyl-1,4-diphenyl-1,4-dihydropyrano[2,3-c]pyrazole-5-carbonitrile and its analogs by electron ionization gas chromatography/mass spectrometry, Journal of Mass Spectrometry, [online], https://doi.org/10.1002/jms.5150, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=958466 (Accessed October 14, 2025)