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

Abstract

It has been established that a chiral S‐shaped [11]helicene‐like molecule can be synthesized with high ee value along with a meso form by the rhodium(I)/(R)‐difluorphos complex‐mediated enantioselective intramolecular double [2+2+2] cycloaddition of a 2‐naphthol‐linked hexayne, even though this chiral helicene has the collision between the terminal benzene rings. Epimerization behavior of the chiral and meso [11]helicene‐like molecules have also been disclosed.

Rhodium‐Catalyzed Enantioselective Synthesis of Highly Fluorescent and CPL‐Active Dispiroindeno[2,1‐c]fluorenes

“…In this context, helicenes, [15–19] heterohelicenes [19,20] and helical compounds [19,21–30] as representatives of SOMs have enjoyed a surge of interest as their twisted molecular structures and inherent helical chirality has been proven as a valuable structural motive for examining CPL properties [31,32] …”

Asymmetric synthesis, structures, and chiroptical properties of helical cycloparaphenylenes

“…3 a These optical properties may be derived from the S-shaped helical structures because those are close to the values of not the CPPs but our previously reported S-shaped double [6]helicene-like molecule ( λ abs = 361 nm, λ lum = 466 nm, Φ F = 48%). 20 …”

“…3a These optical properties may be derived from the S-shaped helical structures because those are close to the values of not the CPPs but our previously reported S-shaped double [6]helicene-like molecule (λ abs = 361 nm, λ lum = 466 nm, Φ F = 48%). 20 To understand the above optical properties, DFT and TDDFT calculations of (Sp D , is extremely large for both 1a and 1b, especially 1a showed a value exceeding 45,000 degree, which is as large as that of [11]helicene. 21,22 The existence of multiple identical helicities in the molecule may induce this large optical rotation value.…”

Rhodium‐Catalyzed Enantioselective Synthesis, Structures, and Properties of Single and Double Azahelicene‐Like Molecules

“…S‐shaped double carbohelicenes E were also synthesized by the same strategy (Figure 1b) [10a] . Recently, S‐shaped double helicene‐like molecule F was synthesized by the rhodium(I)‐catalyzed enantioselective intramolecular double [2+2+2] cycloaddition [12] of a hexayne (Figure 1b) [10b,c] . Importantly, these S‐shaped helical molecules exhibited good chiroptical responses [electronic circular dichroism (ECD) and circularly polarized luminescence (CPL)] as a result of double helicity in the same direction.…”