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Synlett
DOI: 10.1055/a-2705-9249
Letter

I2-Catalyzed Access to Bis(pyrazolo[1,5-a]pyrimidinyl)sulfanes and Sulfenylated Pyrazolo[1,5-a]pyrimidines via C–H Functionalization

Authors

  • Tathagata Choudhuri

    Department of Chemistry, University of Kalyani, Kalyani, India (Ringgold ID: RIN30132)

  • Papiya Sikdar

    Department of Chemistry, University of Kalyani, Kalyani, India (Ringgold ID: RIN30132)

  • Suvam Paul

    Department of Chemistry, University of Kalyani, Kalyani, India (Ringgold ID: RIN30132)

  • Sourav Das

    Department of Chemistry, University of Kalyani, Kalyani, India (Ringgold ID: RIN30132)

  • Avik Kumar Bagdi 

    Department of Chemistry, University of Kalyani, Kalyani, India (Ringgold ID: RIN30132)

Supported by: Department of Science, Technology and Biotechnology (DSTBT), West Bengal, India GO no. 324(Sanc.)/STBT-11012(25)/13/2024-ST SEC
Supported by: Science and Engineering Research Board EEQ/2018/000498
Funding Information A.K.B. acknowledges the Department of Science, Technology and Biotechnology (DSTBT), West Bengal, India (GO no. 324(Sanc.)/STBT-11012(25)/13/2024-ST SEC), ANRF, DST (File no. EEQ/2018/000498), and the University of Kalyani (PRG) for financial support.
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Graphical Abstract

Dedication

This article is dedicated to Prof. S. Chandrasekaran on the occasion of his 80th birthday.

Abstract

We have demonstrated a new route to bis(pyrazolo[1,5-a]pyrimidinyl)sulfanes from pyrazolo[1,5-a]pyrimidines through I2-catalyzed C–H functionalization employing thiourea as the sulfur source. 3-Iodopyrazolo[1,5-a]pyrimidines acted as the active intermediates for this radical C–H sulfenylation. This I2-catalyzed C–H sulfenylation has been extended toward the synthesis of sulfenylated pyrazolo[1,5-a]pyrimidines using sulfonyl hydrazides as sulfenylating agents. Various bis(pyrazolo[1,5-a]pyrimidinyl)sulfanes and sulfenylated pyrazolo[1,5-a]pyrimidines have been synthesized using these simple protocols. The use of easily accessible and bench-stable reactants and reagents, metal-free catalysis, broad substrate scopes, and practicality are the attractive features of this strategy. Moreover, the usefulness of thiourea as a sulfur source in the synthesis of bis(2-phenylimidazo[1,2-a]pyridin-3-yl)sulfane and bis(6-phenylimidazo[2,1-b]thiazol-5-yl)sulfane derivatives has been demonstrated.

Keywords

C–H sulfenylation - Metal-free - Pyrazolo[1,5-a]pyrimidine - Practical - Regioselective

Supplementary Material



Publication History

Received: 18 July 2025

Accepted after revision: 02 September 2025

Accepted Manuscript online:
19 September 2025

Article published online:
05 November 2025

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