Divergent Synthesis of Pyrazoles via Manganese Pincer Complex Catalyzed Acceptorless Dehydrogenative Coupling Reactions

Koushik Sarkar; Pramod Kumar; Arjun Mule; Biplab Maji

doi:10.1002/chem.202401105

Divergent Synthesis of Pyrazoles via Manganese Pincer Complex Catalyzed Acceptorless Dehydrogenative Coupling Reactions

Chemistry. 2024 Apr 24:e202401105. doi: 10.1002/chem.202401105. Online ahead of print.

Authors

Koushik Sarkar¹, Pramod Kumar², Arjun Mule¹, Biplab Maji³

Affiliations

¹ Indian Institute of Science Education and Research Kolkata, Department of Chemical Sciences, INDIA.
² IISER Kolkata Department of Chemical Sciences, Department of Chemical Sciences, INDIA.
³ Indian Institute of Science Education and Research Tirupati, Department of Chemical Sciences, Mohanpur, 741246, Nadia, INDIA.

PMID: 38655822
DOI: 10.1002/chem.202401105

Abstract

This report detailed the synthesis of multi-substituted pyrazoles through the acceptorless dehydrogenative coupling (ADC) reaction catalyzed by a well-defined manganese(I)-pincer complex. Symmetrically substituted pyrazoles were synthesized by reacting 1,3-diols with hydrazines. Unsymmetrically substituted pyrazoles were selectively made via the ADC of primary alcohols with methyl hydrazones. Water and hydrogen are liberated as the green byproducts. The endurance of these methodologies has been presented by producing 30 substrates with varied functionalities. Model reactions were scaled up to demonstrate practicability. The reaction rate and order were measured to transparent the involvement of the reagents during catalysis. Control experiments elucidated the plausible reaction mechanisms.

Keywords: Acceptorless-dehydrogenative coupling; Hydrogen; Manganese catalysis; Pyrazole; Sustainable synthesis.