Reaction between acid N'-(2-oxo-2-phenyl-ethyl)hydrazides, acetylenic esters and alkyl isocyanides in the presence of silica sulfuric acid: One-pot synthesis of highly functionalized 2,3-dihydro-1H-pyrazoles

Abstract

The reactive intermediate produced in the reaction between alkyl isocyanides and dialkyl acetylenedicarboxylates was trapped by acid N'-(2-oxo-2-phenyl-ethyl)hydrazides in the presence of a catalytic amount of silica sulfuric acid (SiO₂-OSO₃H₂) to yield highly functionalized 2,3-dihydro-1H-pyrazoles in good yields. The reaction is characterized by mild conditions and tolerance to various functional groups such as cyclohexyl, t-butyl isocyanides, and Dimethyl-, diethyl- and di-tert-butyl acetylenedicarboxylates.

Graphical Abstract

Keywords:

• Acetylenic esters
• alkyl isocyanides
• three-component reactions
• acid N'-(2-oxo-2-phenyl-ethyl)hydrazides
• silica sulfuric acid