Internal‐Edge‐Substituted Coumarin‐Fused [6]Helicenes: Asymmetric Synthesis, Structural Features, and Control of Self‐Assembly

Abstract

π-Conjugated helicenes containing heteroatoms have attracted significant attention due to their diverse chemical and electronic structures, as well as tunable physical properties. It was rationally anticipated that the self-assembly of coumarin-fused helicenes would be controlled by the effects of a substituent on the internal edge of the helix. Here, this work reports the efficient syntheses of coumarin-fused helicenes 1 a,b (R=Ph, Me), and the enantioselective synthesis of 1 a (R=Ph) by chiral Au -catalyzed hydroarylation. The helical structure of 1 was unambiguously determined by X-ray crystallography. Of particular note, the enantiomerically pure crystal of 1 a adopted a one-dimensional columnar structure based on π-π stacking interactions, as expected. Furthermore, a significant difference between the fluorescence quantum yields of the enantiomerically pure form and racemate of 1 a was observed.

Metal Free Synthesis of Coumarin Containing Hetero[n]helicene like Molecules with TICT and AIE Properties

“…Coumarin containing helical molecules are reported in the literature with fluoroscence property, where coumarin ring was mainly placed at end or both the end of the helical core [37–38] . However quatum yield of those compounds are low as compared to compounds reported in this particular system.…”

“…Heterocyclic fused and π‐extended coumarin compounds have been widely used in optical materials, fluorescent dyes, laser dyes, OLEDs, organic solar cells, etc [31–33] . Surprisingly, there are only a few reports of helicene derivatives comprising of coumarin moiety in extended π‐conjugation and their highly fused conjugated geometry could extend the π‐system to enhance both photophysical and optoelectronic properties [34–38] …”

“…[31][32][33] Surprisingly, there are only a few reports of helicene derivatives comprising of coumarin moiety in extended π-conjugation and their highly fused conjugated geometry could extend the πsystem to enhance both photophysical and optoelectronic properties. [34][35][36][37][38] Coumarin with extended π-conjugation via ortho fused heterocyclic ring can be easily synthesized by the Povarov reaction. Povarov reaction is three component reaction in which aromatic amines initially form aldimines with aldehydes and then undergo [4 + 2] cycloaddition reaction with a variety of substrates including alkyne, alkene, cyclic alkene, enol (ketone, cyclic ketone).…”

Enantioselective Synthesis and Epimerization Behavior of a Chiral S‐Shaped [11]Helicene‐Like Molecule Having Collision between Terminal Benzene Rings

“…In 2007, our research group reported the enantioselective synthesis of single [7]helicene‐like molecules by the cationic rhodium(I)/bisphosphine complex‐catalyzed intramolecular [2+2+2] cycloaddition of triynes . Thus, we designed readily accessible hexayne 3 for the diastereo‐ and enantioselective synthesis of chiral S‐shaped [11]helicene‐like molecule 2 by the intramolecular double [2+2+2] cycloaddition (Scheme ).…”

Synthesis of [7]Helicene Enantiomers and Exploratory Study of Their Conversion into Helically Chiral Iodoarenes and Iodanes

“…[33][34][35][36] Several of these applications necessitate access to optically pure helicenes. [2][3][4] Although af ew asymmetric synthesis approaches have relied on the use of chiral reagents or catalysts, [10,[37][38][39][40][41][42][43][44][45] most of the others were based on substrate controlt hrough the installationo fc hiral moietieso ntom olecular scaffolds prior to their annulation into helicenic systems. [46][47][48][49][50][51][52][53][54][55][56][57][58][59] However,f ully optically pure materials, which are of paramount importance for anya pplication, are rarely obtained, [45][46][47][48][49][50] and diastereoenriched mixtures generated with the help of chiral auxiliaries still need to be separated by conventional chromatography.…”