Description:
<jats:title>Abstract</jats:title><jats:p>Under acylating conditions 3‐acetyl‐4‐hydroxy‐2<jats:italic>H</jats:italic>‐pyran‐2‐one thiosemicarbazones (<jats:bold>1a, b</jats:bold> and <jats:bold>2a, b</jats:bold>) are transformed into 2‐(acylamino)‐5‐methyl‐1,3,4‐thiadiazoles <jats:bold>3b, c, e, f</jats:bold> and 2<jats:italic>H</jats:italic>‐pyran‐2‐ones <jats:bold>1c</jats:bold> and <jats:bold>2c</jats:bold> via C–C bond cleavage. Similarly, the reaction of <jats:bold>1b</jats:bold> with RCO<jats:sub>2</jats:sub>H/EtOH (R = Me, Et) affords 2‐anilino‐5‐methyl‐1,3,4‐thiadiazole (<jats:bold>3d</jats:bold>) and triacetic acid lactone <jats:bold>1c.</jats:bold> Upon treatment with Ac<jats:sub>2</jats:sub>O/Et<jats:sub>3</jats:sub>N the dehydroacetic acid derivative <jats:bold>1b</jats:bold> is transformed into the thiadiazoline <jats:bold>4</jats:bold>, while the benzo derivative <jats:bold>2b</jats:bold> is converted into thiadiazole <jats:bold>3e</jats:bold> and 4‐acetoxycoumarin (<jats:bold>2c</jats:bold>).</jats:p>