A synthesis, characterization and catalytic application of CNT aerogels for conversion of β-nitrostyrenes to arylhydrazones

Abstract

In this study, carbon aerogel was first prepared via the reaction between carbon nanotubes and chitosan. The structure and properties of the prepared carbon aerogel were determined using FESEM, EDS, XRD, FTIR, Raman, TEM, and nitrogen adsorption-desorption isotherm (Based on BET theory). Through the various analyses of the aerogel, due to its mesoporous structure and enriched functional surface, the prepared aerogel was a suitable candidate for catalyzing the reaction. Moreover, there were a few reports on the direct use of carbon-based aerogels as a catalyst. Therefore, the reaction between β-nitrostyrene and hydrazine hydrate was considered for this purpose. This reaction is a retro-aza-Henry type reaction, including non-oxidative C=C double bond cleavage, which is a rare phenomenon in organic reactions. The optimized conditions were obtained using several experiments. Based on these experiments, the best result was obtained using 10 mL ethanol as solvent, 25 ^oC temperature, 30 mg catalyst, and two mmol hydrazine hydrate solution (80%), and in 3 h. According to our experiments, 11 different derivatives of β-nitrostyrene were successfully converted to the corresponding hydrazone in 95-99% yield. The catalyst showed promising results in the reusability experiments, where after six consecutive runs, the yield was reduced by only 5%.

Highlights

·       Metal-free carbon aerogel was prepared and used as a catalyst

·       The reaction between β-nitrostyrene and hydrazine hydrate was performed

·       This studied reaction includes non-oxidative C=C double bond cleavage

·       The reactions were performed at r.t. and completed in 3 h.  

·       11 derivatives of β-nitrostyrene were converted to the hydrazone in 95-99% yield