Helically Chiral Aromatics: The Synthesis of Helicenes by [2 + 2 + 2] Cycloisomerization of π-Electron Systems

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F61388963%3A_____%2F20%3A00519391" target="_blank" >RIV/61388963:_____/20:00519391 - isvavai.cz</a>

Result on the web

<a href="https://pubs.acs.org/doi/abs/10.1021/acs.accounts.9b00364" target="_blank" >https://pubs.acs.org/doi/abs/10.1021/acs.accounts.9b00364</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1021/acs.accounts.9b00364" target="_blank" >10.1021/acs.accounts.9b00364</a>

Result language

angličtina

Original language name

Helically Chiral Aromatics: The Synthesis of Helicenes by [2 + 2 + 2] Cycloisomerization of π-Electron Systems

Original language description

Advanced molecular nanocarbons are now in the spotlight reflecting the basic discoveries of fullerenes, carbon nanotubes, and graphene. This research area includes also the chemistry, physics, and nanoscience of nonplanar polycyclic hydrocarbons, many of which exhibit helical chirality, such as iconic helicenes and their congeners. The combination of unique π-electron systems with the chirality phenomenon makes them highly attractive in various fields of science. Helicenes are polyaromatic compounds that are composed of all-angularly annulated benzene units, but other (hetero)cycles can also be embedded into their backbone. Even though they do not contain any stereogenic center, they are inherently chiral owing to the helical shape they adopt. Hexahelicene and higher homologues are conformationally stable within a reasonable range of temperatures and, therefore, can be obtained in an enantiopure form through a racemate resolution or asymmetric synthesis. An amazing array of synthetic methods for their preparation has been developed, but only a few of them have passed the tough scrutiny to be general, robust and practical methods such as traditional photocyclodehydrogenation of diaryl olefins and recently developed transition-metal-catalyzed [2 + 2 + 2] cycloisomerization of π-electron systems, which is discussed in this Account. Alkyne [2 + 2 + 2] cycloisomerization is a highly exergonic process and is therefore suitable for forming the strained helicene backbone, three (or more) cycles of which are closed in a single operation. The typical starting materials are aromatic triynes (optionally cyanodiynes or ynedinitriles) or tetraynes with diynes that undergo intramolecular or intermolecular cyclization, respectively, catalyzed by various complexes mainly of Ni0, CoI, or RhI. Utilizing this synthetic methodology, various [5]-, [6]-, [7]-, [9]-, [11]-, [13]-, [16]-, [17]-, and [19]helicenes or their congeners, including functionalized derivatives, can be effectively prepared. Moreover, asymmetric synthesis (both catalytic and stoichiometric) of nonracemic helicenes has already been demonstrated. It relies on [2 + 2 + 2] cycloisomerization of centrally chiral triynes followed by an asymmetric transformation of the first order (controlled by the 1,3-allylic-type strain) or on enantioselective [2 + 2 + 2] cycloisomerization of alkynes catalyzed by chiral complexes mainly of Ni0 or RhI. Intriguingly, advanced helical architectures were formed such as the longest helicenes (up to oxa[19]helicene by closing 12 rings in a single synthetic operation) or laterally extended helicenes (e.g., pyreno[7]helicenes). Utilizing the aforementioned synthetic methodology, the tailor-made helical molecular nanocarbons are now better accessible to be applied in enantioselective catalysis, chirality sensing, spintronics (based on chirality induced spin selectivity), chiroptics (to produce circularly polarized light emission), organic/molecular electronics, or chiral single molecule devices.

Czech name

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Czech description

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Type

J_imp - Article in a specialist periodical, which is included in the Web of Science database

CEP classification

—

OECD FORD branch

10401 - Organic chemistry

Project

<a href="/en/project/GA16-08327S" target="_blank" >GA16-08327S: Chiral organic-inorganic hybrid materials and their use in nanoscience</a><br>

Continuities

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Publication year

2020

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Name of the periodical

Accounts of Chemical Research

ISSN

0001-4842

e-ISSN

—

Volume of the periodical

53

Issue of the periodical within the volume

1

Country of publishing house

US - UNITED STATES

Number of pages

15

Pages from-to

144-158

UT code for WoS article

000509420300013

EID of the result in the Scopus database

2-s2.0-85076689756