Helically Chiral 1-Sulfur-Functionalized [6]Helicene: Synthesis, Optical Resolution, and Functionalization

Abstract

The synthesis and optical resolution of helically chiral 5,6,9,10-tetrahydro-1-[6]helicenethiol and its subsequent transformations to enantiopure 1-sulfur-functionalized [6]helicenes are reported. A novel enantiopure [7]thiahelicene having a thiophene ring at the terminal position of the [6]helicene skeleton was synthesized.

Helical nanostructures for organic electronics: the role of topological sulfur in ad hoc synthesized dithia[7]helicenes studied in the solid state and on a gold surface

“…11 To the best of our knowledge, there is however only one example of an endo thiahelicene, namely 1-thia [7]helicene, synthesized only recently from 1-helicenethiol by construction of a new fused thiophene ring attached to the sulfur predetermined position. 12 With this background in mind, we carried out rst the synthesis of the fragments 3 and 4, bearing the desired naphtho[2,1-b]thiophene and naphtho [1,2-b] thiophene ring fusion, as precursors of exo-and endo-dithia [7] helicene-1 and 2, respectively (Scheme 1, see the ESI † for an efficient synthesis of 3 and 4). Ethynylation of 3 and 4 was achieved by means of the Sonogashira reaction using (trimethylsilyl)acetylene followed by desilylation in a basic medium to afford 5 and 6, respectively.…”

Iodine-Containing 4,7-Dihalobenzo[b]thiophene Building Blocks and Related Iodobenzo[b]thiophenes: Promising Molecular Scaffolds for Bio-Inspired Molecular Architecture

“…Preparation of the precursors of this category may be easier than other methods. [90][91][92][93][94][95][96] However, regioselectivity become a problem in specific cases. For example, products 64 and 65 in Scheme 29 were not separated through column chromatographic treatment.…”

Synthesis of (Di)thiahelicenes and Dithiophenohelicenes by [2+2+2] Cycloisomerization of Alkynes

“…[12] In addition to this photochemical synthesis, which is still commonly used today, [13 -15] there is now a whole range of methods to prepare thiahelicenes based also on Diels-Alder cycloaddition (Katz and co-workers), [16] McMurry coupling (Rajca and co-workers [17] or Wang and co-workers [18] ), Scholl reaction (Dehaen and coworkers), [19] double lithiation/sulfanylation (Rajca and co-workers), [20] (electro)chemical oxidative cyclization (Larsen and co-workers [21] or Pei and co-workers [22] ), electrophilic sulfanylation (Nishide and co-workers), [23] Pd-catalyzed annulation with alkynes (Cauteruccio and co-workers), [15] Pt-promoted hydroarylation of alkynes (Cauteruccio and co-workers) [15] and Friedel-Craftstype cyclization (Gaucher, Prim and co-workers, [24] Guégan, Prim, Salpin and co-workers [25] ) or cycloannulation (Tsujihara, Kawano and co-workers). [26] Transition metal complexes-catalyzed [2 + 2 + 2] cycloisomerization of alkynes developed by Stará and Starý [27] has recently gained increasing popularity due to its robustness, versatility and possible stereocontrol in the synthesis of helicenes and their congeners. This methodology allows the construction of not only parent carbohelicenes but also their N-, [10,[28][29][30][31][32][33][34] O-, [10,[35][36][37] Si- [38,39] or P-heterocyclic analogues.…”