Synthesis of New 2-Phenylpyrano[3,2-b]phenothiazin-4(6H)-one Derivatives
摘要:
AbstractA new synthesis of 2‐phenylpyrano[3,2‐b]phenothiazin‐4(6H)‐one derivatives was reported. First 2,10‐diacetyl‐3‐hydroxyphenothiazine (2) was converted into their benzoyloxy esters (3a–3j) using different aromatic carboxylic acids in the presence of phosphorous oxychloride in pyridine. Benzoyloxy esters were converted into their 1,3‐diones (4a–4j) by using dry KOH in pyridine via Baker‐Venkataraman transformation reaction. The 1,3‐diones thus obtained were cyclised to pyranophenothiazines (5a–5j) by refluxing in an acetic acid/HCl mixture.