Dimethylurea/L-tartaric acid as deep eutectic solvent for one-pot synthesis of 2-(methylamino)-3-nitrospiro-[chromene] and N-methyl-3-nitro-4H chromen-2-amines

Abstract

An application of dimethyl urea and L-tartaric acid as deep eutectic solvent (DES) is demonstrated for the synthesis of 2-(methylamino)-3-nitrospiro[chromene] and N-methyl-3-nitro-4H-chromen-2-amines by a reaction of substituted isatins/pyrazole aldehydes, nucleophiles and (E)-N-methyl-1-(methylthio)-2-nitroethenamine. Systematic studies proved that the dimethyl urea and L-tartaric acid in 2:1 ratio at 80 °C is suitable to give the desired products in good yields in shorter period of reaction time (45 min). This method was extended for water as reaction medium and good yields of the products was obtained in 1 h.

Graphical Abstract

Keywords:

• Chromenes
• catalyst-free
• deep eutectic solvent (DES)
• spirooxindoles
• water

Additional information

Funding

KS thanks DST for the INSPIRE fellowship. SN thanks, UGC-New Delhi for the fellowship. DK thanks, DST (SERB), New Delhi for the financial support [SB/FT/CS-136/2012 and SB/EMEQ-103/2014].