An efficient metal-free and catalyst-free C-S/C-O bond-formation strategy: synthesis of pyrazole-conjugated thioamides and amides

Shubham Sharma; Dharmender Singh; Sunit Kumar; Vaishali; Rahul Jamra; Naveen Banyal; Deepika; Chandi C Malakar; Virender Singh

doi:10.3762/bjoc.19.22

An efficient metal-free and catalyst-free C-S/C-O bond-formation strategy: synthesis of pyrazole-conjugated thioamides and amides

Beilstein J Org Chem. 2023 Mar 2:19:231-244. doi: 10.3762/bjoc.19.22. eCollection 2023.

Authors

Shubham Sharma¹, Dharmender Singh^{1

2}, Sunit Kumar¹, Vaishali¹, Rahul Jamra^{1

3}, Naveen Banyal^{1

3}, Deepika¹, Chandi C Malakar⁴, Virender Singh^{1

3}

Affiliations

¹ Department of Chemistry, Dr B R Ambedkar National Institute of Technology (NIT) Jalandhar, 144027, Punjab, India.
² Central Revenues Control Laboratory, New Delhi-110012, India.
³ Department of Chemistry, Central University of Punjab, Bathinda, 151401, Punjab, India.
⁴ Department of Chemistry, National Institute of Technology (NIT) Manipur, Imphal, 795004, India.

Abstract

An operationally simple and metal-free approach is described for the synthesis of pyrazole-tethered thioamide and amide conjugates. The thioamides were generated by employing a three-component reaction of diverse pyrazole C-3/4/5 carbaldehydes, secondary amines, and elemental sulfur in a single synthetic operation. The advantages of this developed protocol refer to the broad substrate scope, metal-free and easy to perform reaction conditions. Moreover, the pyrazole C-3/5-linked amide conjugates were also synthesized via an oxidative amination of pyrazole carbaldehydes and 2-aminopyridines using hydrogen peroxide as an oxidant.

Keywords: C–S/O bond formation; metal-free; oxidative amidation; pyrazole carbaldehydes; sulfur insertion; thioamides.

Grants and funding

S.S. acknowledges the Ministry of Human Resource Development (MHRD), New Delhi, India, and CSIR, New Delhi for Junior Research Fellowships. S. K. and V. S. gratefully acknowledges the financial support in the form of research grants from CSIR (02 (0202) /14/EMR-II), DST (CS-361/ 2011), and DST-FIST (CSI-228/2011) New Delhi (India).