Addition of Thiocyanic Acid to Chalcones: Practical Synthesis of 1,3-Diaryl-3-isothiocyanatopropan-1-ones

Anatoly Shutalev,Anastasia Fesenko,Pavel Solovyev

doi:10.3390/ecsoc-20-a017

Abstract

Highlights

Chalcones 3a-i which were readily prepared by base-catalyzed condensation of the corresponding acetophenones and aromatic aldehydes were used as starting materials.[15]
They reacted with aqueous thiocyanic acid generated in situ by treatment of thiocyanate ammonium with dilute sulfuric acid to give the target 1,3-diaryl-3-isothiocyanatopropan-1-ones 4a-i (Scheme 1)
Since aqueous solutions of HNCS were reported to be unstable at high concentrations,[16] with chalcone 3c we tried the addition of NH4NCS to the reaction mixture in portions, but this had no effect on the isolated yield of 4c

Summary

Introduction

Practical synthesis of 1,3-diaryl-substituted 3-isothiocyanatopropan-1-ones based on the reaction of chalcones with thiocyanic acid generated in situ by treatment of thiocyanate ammonium with dilute sulfuric acid has been developed. NH4NCS molar ratio = 1:1:3.3, water, rt, 3 h).[12] according to 1H NMR spectroscopic data, the crude product contained 95% of the starting material and only 5% of isothiocyanate 2. With low-melting chalcone 3a (mp 56–57 °C) emulsion was obtained by heating the reaction mixture at 50 °C without addition of AcOH, but still only trace amount of isothiocyanate 4a formed (entry 2).

Results

Conclusion