Functionalized 10(2,4,6‐Triarylphenyl)‐10 H ‐phenothiazines Synthesized Without Metal Catalysts

A new synthetic approach to functionalized N ‐(2,4,6‐triarylphenyl) phenothiazines is presented. The methodology is based on a modified Fischer–Zimmermann condensation of triaryl pyrylium salts with aryl acetates, specifically sodium β ‐ N ‐phenothiazine acetate, and affords sterically highly congested compounds. Single‐crystal X‐ray analyses of several of these compounds reveal that the pronounced steric hindrance results in an almost perpendicular orientation between the triaryl phenyl moiety ring and the phenothiazine core, accompanied by a significantly reduced folding angle of the latter. These structural arrangements also correlate with the low oxidation potential of the compounds.