Contractive Annulation: A Strategy for the Synthesis of Small, Strained Cyclophanes and Its Application in the Synthesis of [2](6,1)Naphthaleno[1]paracyclophane

Biswas, Sourav; Qiu, Christopher S.; Zhao, Yuming; Bodwell, Graham J.

doi:10.1002/ange.201904673

Cited by 4 publications

(8 citation statements)

References 31 publications

(16 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“… An alternative approach, involving the incorporation of acenes into cyclophanes using a diagonal tether, has not been commonly applied. Otsubo et al and Haenel et al used this approach to obtain 2,6-tethered naphthalenes as either a single bridge cyclophane, 8 , or triple decker cyclophane, 9 , respectively, with a dihedral twist of up to 32°. , Very recently, Bodwell et al introduced contractive annulation as a new synthetic approach for strained cyclophanes and demonstrated this approach for the synthesis of asymmetric naphthalenophane. The work of Bodwell, Otsubo and Haenel, inspired us to helically lock pretwisted anthracene by using diagonal tethers of different lengths to achieve various backbone twist angles.…”

Section: Synthesis and Strainmentioning

confidence: 99%

See 1 more Smart Citation

The Consequences of Twisting Nanocarbons: Lessons from Tethered Twisted Acenes

Bedi

Gidron

2019

Acc. Chem. Res.

View full text Add to dashboard Cite

Conspectus The properties of polycyclic aromatic hydrocarbons are determined by their size, shape, and functional groups. Equally important is their curvature, since deviation from planarity can affect their optical, electronic, and magnetic properties and also induce chirality. Acenes, which can be viewed as one-dimensional nanocarbons, are often twisted out of planarity. Although twisting is expected to affect the above-mentioned properties, it is often overlooked. This Account focuses on helically locked twistacenes (twisted acenes) having different twist angles and the effect of twisting on their electronic and optical properties. Various synthetic approaches to inducing backbone twist in acenes are discussed, with a focus on the introduction of a diagonal tether across the core, as this minimizes confounding substituent effects. Using such tethered acenes as our model, we then discuss the effects of twisting the aromatic core on twistacene properties. Electronic properties. Increasing the degree of twist only slightly affects the HOMO and LUMO energy levels. Twisting leads to a small increase in the HOMO level and a decrease in the LUMO level, which produces an overall decrease in the HOMO–LUMO gap. Optical properties. As the degree of twist increases, a slight bathochromic shift is observed in the absorption spectra, in accordance with the decrease in the HOMO–LUMO gap. The fluorescence quantum efficiency and the fluorescence lifetime also decrease. This is likely to be related to an increasing rate of intersystem crossing, which arises from increased spin–orbit coupling. In addition, computational studies indicate that the S0–T1 energy gap decreases with increasing twist. Chiroptical properties. Increased twisting results in a larger Cotton effect and anisotropy factor, with the anisotropy factors of Ant-Cn being higher than those of longer helicenes. The parallel orientation of electric and magnetic transition dipole moments in twistacenes underlies this behavior and renders them as excellent chiroptical materials. The same trend is observed for the radical cations of twistacenes, which absorb in the NIR spectral region. Conjugation and delocalization. Twisting the anthracene radical cation up to 40° (13° per benzene ring) does not significantly affect spin delocalization, with the EPR spectra of twistacene radical cations showing that only slight localization occurs. This is in line with computational studies, which show only a small decrease in π-overlap for large acene twist. Overall, modifying the length of the tether in diagonally tethered acenes allows chemists to control core twist and to induce chirality. Twisting affects key optical, electronic, and chiroptical properties of acenes. Consequently, controlling the twist angle can improve the future design of nanocarbons with desired properties.

show abstract

Section: Synthesis and Strainmentioning

confidence: 99%

“…Exploring systems larger than acenes, Bodwell demonstrated that the HOMO level increases as the degree of bending increases in pyrenes . Recently, Müllen, Narita, and co-workers demonstrated that the band gap of graphene nanoribbons can be reduced by distorting them from planarity .…”

Section: The Effects Of Core Twistingmentioning

confidence: 99%

The Consequences of Twisting Nanocarbons: Lessons from Tethered Twisted Acenes

Bedi

Gidron

2019

Acc. Chem. Res.

View full text Add to dashboard Cite

show abstract

“…The naphthalene twist angles for 14 and 15 were not reported, but have now been determined using the original data to be substantially lower than those in 13 (9.7°a nd 9.5°for 14; 7.5°and 4.3°for 15). On the other hand, the values for 13 are well short of those observed in more highly strained systems such as 1,7-dioxa [7](2,7)pyrenophane (16, 37°) 14 and [2](6,1)naphthaleno [1]paracyclophane (17, 35.1°) 15 both of which required powerful aromatizationbased methods for their synthesis.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“Shadow” Synthesis, Structure, and Electronic Properties of [2.2](1,6)(1,8)Pyrenophane-1-monoene

et al. 2021

Self Cite

View full text Add to dashboard Cite

An unexpected side product of a McMurry reaction was found to be a new [2.2]pyrenophane consisting of two pyrene units with different substitution patterns as well as different types and degrees of distortion from planarity. The new pyrenophane exhibits both monomer and intramolecular excimer fluorescence. Natural bond orbital (NBO) analysis revealed that there is an intramolecular charge-transfer interaction from the more distorted pyrene system to the less distorted one. The origin of the new pyrenophane was traced back to an impurity that was present a full five steps prior to the McMurry reaction from which it was isolated. The pathway to the pyrenophane shadowed that of the main synthetic route.

show abstract

“…

…”

mentioning

confidence: 99%

“…The use of a bridge C(sp 3 ) atom in the benzannulation means that the growth of the aromatic system is accompanied by a shortening of the bridge and an increase in molecular strain. The utility of CA was first demonstrated in the synthesis of [2](6,1)naphthaleno [1]paracyclophane (2) in 9 steps from [2.2]paracyclophane (1). 1 Reported here is a double CA of 1 to afford [1.1]naphthalenophane 3, which joins the very small family of [1.1]cyclophanes.…”

mentioning

confidence: 99%

Synthesis of anti-[1](1,6)Naphthaleno[1](1,6)naphthalenophane by Double Contractive Annulation of [2.2]Paracyclophane

et al. 2022

Self Cite

View full text Add to dashboard Cite

Two-directional contractive annulation of [2.2]paracyclophane has led to the synthesis of anti- [1](1,6)naphthaleno [1](1,6)naphthalenophane (3). This [1.1]cyclophane (SE = 56.6 kcal/mol) consists of two bent and twisted naphthalene units with interplanar distances as short as 2.74 Å. Despite the high strain and structural distortion, 3 was found to be unreactive toward potential cycloaddition partners (TCNE, DMAD) and under UV irradiation.C ontractive annulation (CA) was recently developed as a new strategy for the synthesis of small, strained cyclophanes. 1 It involves the benzannulation of an existing cyclophane using a set of three carbon atoms: a benzylic C(sp 3 ) atom, the bridgehead (ipso) C(sp 2 ) atom to which it is bonded and a neighboring (ortho) C(sp 2 ) atom (Scheme 1).

show abstract

Contractive Annulation: A Strategy for the Synthesis of Small, Strained Cyclophanes and Its Application in the Synthesis of [2](6,1)Naphthaleno[1]paracyclophane

Abstract: A new synthetic strategy (contractive annulation) for the synthesis of highly strained cyclophanes has been conceived and its viability has been demonstrated through a nine‐step synthesis of [2](6,1)naphthaleno[1]paracyclophane from [2.2]paracyclophane.

Cited by 4 publications

References 31 publications

The Consequences of Twisting Nanocarbons: Lessons from Tethered Twisted Acenes

The Consequences of Twisting Nanocarbons: Lessons from Tethered Twisted Acenes

“Shadow” Synthesis, Structure, and Electronic Properties of [2.2](1,6)(1,8)Pyrenophane-1-monoene

Synthesis of anti-[1](1,6)Naphthaleno[1](1,6)naphthalenophane by Double Contractive Annulation of [2.2]Paracyclophane

Contact Info

Product

Resources

About