Microwave‐assisted decarboxylation of 2H‐Pyran‐3‐carboxylic acid derivatives under basic condition

Abstract

Despite the availability of several methods for decarboxylation, this area remains exploratory and requires new development. Here, we report a highly efficient microwave‐assisted hydrodecarboxylation of 4‐(methylthio)‐2‐oxo‐6‐aryl‐2H‐pyran‐3‐carboxylic acids (1a‐k) under basic condition to obtain 4‐(methylthio)‐6‐aryl‐2H‐pyran‐2‐ones (2a‐k) with >90% yield. The requirement of proton source from the solvent was observed by performing the reactions of 1b and 1e in CD3OD to obtain deuterated compounds 2 l and 2 m respectively. All compounds were characterized by spectroscopic analysis. Further, compounds 2b and 2e were analyzed by single‐crystal X‐ray diffraction studies.

Amidate ion‐mediated intramolecular ring transformation of 2‐pyrones to 2‐pyridones

“…The reaction was quenched with methanol, the crude was purified, and characterized spectroscopically as the ring‐transformed product 2a (Scheme 1) in 78% yield. Recently, we reported the decarboxylation of 2‐pyrone carboxylic acid derivatives by treating them with KOH in methanol at RT and under microwave conditions [12]. Thus, we became interested in checking whether the 2‐pyridone carboxylic acid ( 2a ) will undergo decarboxylation under basic conditions.…”