Synthesis and Stereochemical Properties of Chiral Hetero[7]helicenes Structured by a Benzodiheterole Ring Core

Arae, Sachie; Mori, Takaaki; Kawatsu, Takahiro; Ueda, Daiki; Shigeta, Yusuke; Hamamoto, Nobutsugu; Fujimoto, Hitoshi; Sumimoto, Michinori; Imahori, Tatsushi; Igawa, Kazunobu; Tomooka, Katsuhiko; Punniyamurthy, Tharmalingam; Irie, Ryo

doi:10.1246/cl.170410

Cited by 9 publications

(7 citation statements)

References 71 publications

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“…Regioselectivity of the photocyclization to 139a. 170 (see also 171 ). Significantly, 142 was stereochemically stable at room temperature and could be enantiomerically resolved by chiral HPLC using Chiralcel IC (eluent: hexane/THF = 9/1).…”

Section: Carbazoles From Oxidative Photocyclizationmentioning

confidence: 94%

“…Carbazoles from Palladium-Catalyzed Cyclodehydrogenation. A new hetero [7]helicene 142 (Scheme 36) incorporating a diazabenzo ring core 165 was successfully synthesized by Ryo Irie et al by a catalytic domino cyclodehydrogenation using Pd(OAc) 2 and O 2 as the key step 170 (see also ref 171). Significantly, 142 was stereochemically stable at room temperature and could be enantiomerically resolved by chiral HPLC using Chiralcel IC (eluent: hexane/THF = 9/1).…”

Section: Chemical Reviewsmentioning

confidence: 99%

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Enantioenriched Helicenes and Helicenoids Containing Main-Group Elements (B, Si, N, P)

2019

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In this review, we discuss the rich chemistry of helicenes and helicenoids containing maingroup elements. Enantioenriched helicenic derivatives containing main-group elements B, Si, N and P, either incorporated within the helical backbone or grafted to it, will be thoroughly presented. We will describe their synthesis, resolution, and asymmetric synthesis, their structural features, electronic and chiroptical properties, emission, together with other photochemical properties and applications. OUTLINE 14 The absorption spectrum of 19c recorded in CH 2 Cl 2 solutions exhibited a maximum at 376 nm which is significantly red shifted compared with that of double [5]helicene 19a (310 nm) due to the more extended π-conjugation in 19c. According to TD-DFT calculations, the low-energy absorption band from 400 to 500 nm is assignable to the HOMO→LUMO transition corresponding to a π−π* transition of the fully conjugated bis-helical system. DFT calculations revealed a very high theoretical isomerization barrier of 45.1 kcal/mol for the (P,P)/(M,M)-19c stereoisomer, i.e. 4.4 kcal/mol higher than the (P,M) stereoisomer (not observed experimentally). The high configurational stability of 19c enabled to obtain the pure (P,P)and (M,M)-19c by chiral HPLC (Daicel Chiralcel IE column; EtOAc/MeOH = 9:1 as eluent) and to study their chiroptical properties. The ECD spectrum of (P,P)-19c in CH 2 Cl 2 displayed two strong positive bands at 275 and 320 nm, a strong negative one at 375 nm and a broad and less intense one between 425-475 nm. 52 Note that the isomerization barrier of the OBO-fused double [7]helicene is much higher than for oxabora[6]helicene 9 (vide supra) and higher than carbo[7]helicene (42.0 kcal/ mol), indicating the advantage of double helicenes over monohelicenes in terms of conformational stability. Indeed no racemization was observed upon heating enantiomer (P,P) and (M,M)-19c for 24 h up to 200 °C. 52 Note that in 2017 a longer double OBO-helicene analogue was deposited on a Au(111) under UHV conditions and its surface-assisted cyclodehydrogenation into a planar OBO-perihexacene was observed by STM. 54 Similarly to 6 and 9, the strong bond alternation found in the BOC4 rings of 19a 51 may account for the small NICS value of 1.3 while the surrounding C6 rings, including the distorted central benzene ring, show large negative NICS values (Scheme 3c). For comparison, in the all-carbon analogue tetrabenzo-[a,f,j,o]perylene shown in Scheme 3c, the central C6 ring shows a positive NICS value, indicating substantial antiaromatic character. Notably, molecular orbital calculations of 19a indicate that the HOMO and LUMO are spread over the C6 rings rather than on the boron and oxygen atoms, accounting for the substantial stability of 19a (Scheme 3c). Borahelicenes are efficient blue fluorophores. Indeed, azabora[6]helicene 6 displays blue fluorescence at 447 nm (Table 2), while smaller achiral [4]helicenic systems were successfully used as host materials in phosphorescent OLEDs with efficiencies better than the classical 4,4'...

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Section: Carbazoles From Oxidative Photocyclizationmentioning

confidence: 94%

Section: Chemical Reviewsmentioning

confidence: 99%

Enantioenriched Helicenes and Helicenoids Containing Main-Group Elements (B, Si, N, P)

2019

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“…517 As a further recent development, chiral hetero [7]helicenes based on the benzo [a]indolo[2,3-c]carbazole core have been prepared and studied. 518 Structurally related systems featuring an indolo[2,3-c]carbazole fused to a quinoline have also been reported as products from a palladium-catalyzed reductive annulation of a bis(2-nitrophenyl)carbazole precursor in the presence of hydrogen. 281 In an approach of rather limited scope, the indolo[2,3c]carbazole 400 was obtained as the only successful example upon cyclization of the precursor 401 in the presence of a ruthenium catalyst and tetraethylammonium chloride (Scheme 90).…”

Section: Indolo[32-b]carbazole Polymersmentioning

confidence: 99%

“…In a later study, the N -butyl substituted analogue of 398 was converted to twin donor systems featuring 1,3-propylene or m -xylylene bridges between the benzo[ a ]indolo[2,3- c ]carbazole motifs . As a further recent development, chiral hetero[7]helicenes based on the benzo[ a ]indolo[2,3- c ]carbazole core have been prepared and studied . Structurally related systems featuring an indolo[2,3- c ]carbazole fused to a quinoline have also been reported as products from a palladium-catalyzed reductive annulation of a bis(2-nitrophenyl)carbazole precursor in the presence of hydrogen …”

Section: Indolo[23-c]carbazolesmentioning

confidence: 99%

Chemistry and Properties of Indolocarbazoles

et al. 2018

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The indolocarbazoles are an important class of nitrogen heterocycles which has evolved significantly in recent years, with numerous studies focusing on their diverse biological effects, or targeting new materials with potential applications in organic electronics. This review aims at providing a broad survey of the chemistry and properties of indolocarbazoles from an interdisciplinary point of view, with particular emphasis on practical synthetic aspects, as well as certain topics which have not been previously accounted for in detail, such as the occurrence, formation, biological activities, and metabolism of indolo[3,2- b]carbazoles. The literature of the past decade forms the basis of the text, which is further supplemented with older key references.

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“…Considering the importance of the elucidation of structure–property relationship for molecular designs to develop useful heterohelicenes, there remains ample room to develop new synthetic approaches to heterohelicenes with higher efficiency and structural diversity including kinds and positions of endocyclic heteroatoms and numbers of constituent rings. 8 …”

Section: Introductionmentioning

confidence: 99%

Asymmetric systematic synthesis, structures, and (chir)optical properties of a series of dihetero[8]helicenes

2021

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Synthesis and Stereochemical Properties of Chiral Hetero[7]helicenes Structured by a Benzodiheterole Ring Core

Cited by 9 publications

References 71 publications

Enantioenriched Helicenes and Helicenoids Containing Main-Group Elements (B, Si, N, P)

Enantioenriched Helicenes and Helicenoids Containing Main-Group Elements (B, Si, N, P)

Chemistry and Properties of Indolocarbazoles

Asymmetric systematic synthesis, structures, and (chir)optical properties of a series of dihetero[8]helicenes

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