Facile Synthesis Of 5-Arylidene Rhodanine Derivatives Using Na2so3 As An Eco-Friendly Catalyst. Access To 2-Mercapto-3-Aryl-Acrylic Acids And A Benzoxaborole Derivative

A simple, efficient and environment-friendly procedure for the synthesis of 5-arylidene rhodanines derivatives via a Knoevenagel type reaction was developed using rhodanine, a variety of differently substituted aldehydes and Na2SO3 as benign catalyst in ethanol. Selected 5-arylidene rhodanines were subjected to basic hydrolysis to afford 2-mercapto-3-substituted-acrylic acids. The presence of a boronic acid group is well tolerated in such transformations. In the case of 2-formylphenylboronic acid, this sequence opens access to a new benzoxaborole derivative. (C) 2020 Elsevier Ltd. All rights reserved.