Thia‐Bridged Triarylamine Hetero[4]Helicenes: Regioselective Synthesis and Functionalization

Abstract

Thia‐bridged triarylamine hetero[4]helicenes (TBTH[4]H) are a peculiar class of geometrically stable [4]helicenes that have shown promising applications as organic electronic materials. Their structure comprises a bis‐phenothiazine moiety, with a nitrogen atom and an aromatic ring in common, forced into a helix‐shaped arrangement by four carbon–sulfur bonds. We describe a detailed study on the scope and application of the electrophilic sulfur insertion path to TBTH[4]H, with particular emphasis on the regioselective preparation of asymmetric (not dissymmetric) derivatives.

SET and HAT/PCET acid‐mediated oxidation processes in helical shaped fused bis‐phenothiazines

“…We have settled a new and more feasible procedure for the preparation of these systems based on the regioselective sulfenylation with phthalimidesulfenyl chloride PhtNSCl (Pht=Phthaloyl) of triarylamines or N ‐aryl phenothiazines followed by a second Lewis acid promoted internal electrophilic sulfenylation [8,10] . Recently, this procedure was further optimized for the preparation of asymmetric (not dissymmetric) derivatives [18] . For this study we selected thia[4]heterohelicenes 1 – 9 (Figure 2, top) that were designed to have an identical phenothiazine sub‐unit (the red‐boxed left segment in Figure 1) and a differently substituted sub‐unit (the blue‐boxed right segment in Figure 1).…”

“…For this study we selected thia[4]heterohelicenes 1 – 9 (Figure 2, top) that were designed to have an identical phenothiazine sub‐unit (the red‐boxed left segment in Figure 1) and a differently substituted sub‐unit (the blue‐boxed right segment in Figure 1). Compounds 1 – 4 were prepared as previously described [8,10,18] . Hydroxy substituted derivatives 5 , 6 and 7 , are the result of BBr 3 demethylation of the corresponding methoxy substituted helicenes 2 , 3 and 4 (Figure 2 middle and experimental section).…”

“…[ 8 , 10 ] Recently, this procedure was further optimized for the preparation of asymmetric (not dissymmetric) derivatives. [18] For this study we selected thia[4]heterohelicenes 1 – 9 (Figure 2 , top) that were designed to have an identical phenothiazine sub‐unit (the red‐boxed left segment in Figure 1 ) and a differently substituted sub‐unit (the blue‐boxed right segment in Figure 1 ). Compounds 1 – 4 were prepared as previously described.…”

“…Compounds 1 – 4 were prepared as previously described. [ 8 , 10 , 18 ] Hydroxy substituted derivatives 5 , 6 and 7 , are the result of BBr 3 demethylation of the corresponding methoxy substituted helicenes 2 , 3 and 4 (Figure 2 middle and experimental section). New hydroxy substituted bis‐phenothiazines 8 and 9 were prepared, as previously mentioned, from the corresponding properly designed N‐aryl phenothiazines (Figure 2 bottom, experimental and Supplementary Information sections).…”

“…Phthalimide sulfenyl chloride was prepared from the corresponding disulfide as reported elsewhere [8] . Helicenes 1 , 2 , 3 and 4 were described elsewhere [8,18] . Preparation of the starting materials for the synthesis of helicenes 8 and 9 is available as Supplementary Information.…”