Solvent-Free One-Pot Synthesis of Sulfonephthaleins from Saccharin and Phenols

Abstract

Sulfonephthaleins can be synthesized in a single pot from saccharin and phenol via the in situ formation of 2-sulfobenzoic anhydride, followed by its reaction with phenol using H₂SO₄ as the condensing agent, in the absence of any solvent. This solvent-free synthesis is more economical and environmentally benign.

GRAPHICAL ABSTRACT

Keywords:

• H₂SO₄
• phenols
• saccharin
• sulfonephthalein

ACKNOWLEDGMENT

V. R. C. and D. K. D. are grateful to the National Academy of Sciences, India, for the Senior Scientist Platinum Jubilee Fellowship and Project Assistantship, respectively.

Notes

^a Yields indicated here are isolated yields. Phenol red is water soluble and could not be fully recovered after workup.

^a BF₃ etherate, Dowex-50, Amberlyst-15, HCl, Hβ zeolite, HY zeolite, or ZnCl₂.