Metal-Free α-Sulfonylation of β-Ketothioamides: Access to α-Sulfonyl-β-Ketoamides and their Photophysical Studies

Herein, we report a metal and additive-free unprecedented reactivity of β-ketothioamides with sulfonyl chlorides for the synthesis of previously unreported 2-sulfonyl-3-oxo-N,3-diarylpropanamides via in situ thioamide to amide conversion followed by dehydrohalogenative C-S cross-coupling at room temperature under an open air for the first time. The protocol demonstrates not only its operational simplicity, efficiency, mild condition, and scalability, but also easy to get the diverse α-sulfonyl-β-ketoamides in good to high yields. Additionally, the DFT and photophysical studies supported the proposed mechanism, and revealed unique excitation-dependent emission coupled with ESPT for the synthesized sulfones.