Carbo[n]helicenes Restricted to Enantiomerize: An Insight into the Design Process of Configurationally Stable Functional Chiral PAHs

Overview

Journal Chemistry

Specialty Chemistry

Date 2020 Oct 9

PMID 33034405

Citations 19

Authors

Prince Ravat

Affiliations

Soon will be listed here.

Abstract

The most important stereodynamic feature of carbo[n]helicenes is the interconversion of their enantiomers. The Gibbs activation energy (ΔG (T)) of this process, which determines the rate of enantiomerization, dictates the configurational stability of [n]helicenes. High values of ΔG (T) are required for applications of functional chiral molecules incorporating [n]helicenes or helicene substructures. This minireview provides an overview of the mechanism, recent developments, and factors affecting the enantiomerization of [n]helicenes, which will accelerate the design process of configurationally stable functional chiral molecules based on helicene substructures. Additionally, this minireview addresses the misconception and irregularities in the recent literature on how the terms "racemization" and "enantiomerization" are used as well as how the activation parameters are calculated for [n]helicenes and related compounds.

Citing Articles

Twisted Nanographenes with Robust Conformational Stability.

Song P, Hashikawa Y, Chaolumen Nanomaterials (Basel). 2024; 14(21).

PMID: 39513817 PMC: 11547671. DOI: 10.3390/nano14211737.

Synthesis, Structures, and Chiroptical Properties of NBN-Doped Helicenes with Boron Atoms in the Inner Rims.

Zhuang W, Liu Y, Deng Z, Guo Y, Chow P, Lee Phillips D Precis Chem. 2024; 2(1):28-39.

PMID: 39474568 PMC: 11504388. DOI: 10.1021/prechem.3c00097.

Helically twisted nanoribbons stereospecific annulative π-extension reaction employing [7]helicene as a molecular wrench.

Swain A, Radacki K, Braunschweig H, Ravat P Chem Sci. 2024; 15(30):11737-11747.

PMID: 39092091 PMC: 11290328. DOI: 10.1039/d4sc01814a.

Copper-catalysed perarylation of cyclopentadiene: synthesis of hexaarylcyclopentadienes.

Gisbert Y, Simon Marques P, Baccini C, Abid S, Saffon-Merceron N, Rapenne G Chem Sci. 2024; 15(24):9127-9137.

PMID: 38903211 PMC: 11186316. DOI: 10.1039/d4sc02458c.

Boosting quantum yields and circularly polarized luminescence of penta- and hexahelicenes by doping with two BN-groups.

Appiarius Y, Miguez-Lago S, Puylaert P, Wolf N, Kumar S, Molkenthin M Chem Sci. 2024; 15(2):466-476.

PMID: 38179512 PMC: 10762774. DOI: 10.1039/d3sc02685j.

References

Jancarik A, Rybacek J, Cocq K, Chocholousova J, Vacek J, Pohl R . Rapid access to dibenzohelicenes and their functionalized derivatives. Angew Chem Int Ed Engl. 2013; 52(38):9970-5. DOI: 10.1002/anie.201301739. View

Randic M . Aromaticity of polycyclic conjugated hydrocarbons. Chem Rev. 2003; 103(9):3449-605. DOI: 10.1021/cr9903656. View

Yamamoto K, Okazumi M, Suemune H, Usui K . Synthesis of [5]helicenes with a substituent exclusively on the interior side of the helix by metal-catalyzed cycloisomerization. Org Lett. 2013; 15(8):1806-9. DOI: 10.1021/ol400332j. View

Rickhaus M, Mayor M, Juricek M . Strain-induced helical chirality in polyaromatic systems. Chem Soc Rev. 2016; 45(6):1542-56. DOI: 10.1039/c5cs00620a. View

Han S, Bond A, Disch R, Holmes D, Schulman J, Teat S . Total syntheses and structures of angular [6]- and [7]phenylene: the first helical phenylenes (heliphenes). Angew Chem Int Ed Engl. 2002; 41(17):3223-7. DOI: 10.1002/1521-3773(20020902)41:17<3223::AID-ANIE3223>3.0.CO;2-G. View

Sawada Y, Furumi S, Takai A, Takeuchi M, Noguchi K, Tanaka K . Rhodium-catalyzed enantioselective synthesis, crystal structures, and photophysical properties of helically chiral 1,1'-bitriphenylenes. J Am Chem Soc. 2012; 134(9):4080-3. DOI: 10.1021/ja300278e. View

Portella G, Poater J, Bofill J, Alemany P, Sola M . Local aromaticity of [n]acenes, [n]phenacenes, and [n]helicenes (n = 1-9). J Org Chem. 2005; 70(7):2509-21. DOI: 10.1021/jo0480388. View

Schoetz G, Trapp O, Schurig V . Determination of the enantiomerization barrier of thalidomide by dynamic capillary electrokinetic chromatography. Electrophoresis. 2001; 22(15):3185-90. DOI: 10.1002/1522-2683(200109)22:15<3185::AID-ELPS3185>3.0.CO;2-V. View

Mori K, Murase T, Fujita M . One-step synthesis of [16]helicene. Angew Chem Int Ed Engl. 2015; 54(23):6847-51. DOI: 10.1002/anie.201502436. View

10.

Chandra Mondal P, Fontanesi C, Waldeck D, Naaman R . Spin-Dependent Transport through Chiral Molecules Studied by Spin-Dependent Electrochemistry. Acc Chem Res. 2016; 49(11):2560-2568. PMC: 5112609. DOI: 10.1021/acs.accounts.6b00446. View

11.

Hartung T, Machleid R, Simon M, Golz C, Alcarazo M . Enantioselective Synthesis of 1,12-Disubstituted [4]Helicenes. Angew Chem Int Ed Engl. 2020; 59(14):5660-5664. PMC: 7154633. DOI: 10.1002/anie.201915870. View

12.

Osswald P, Wurthner F . Effects of bay substituents on the racemization barriers of perylene bisimides: resolution of atropo-enantiomers. J Am Chem Soc. 2007; 129(46):14319-26. DOI: 10.1021/ja074508e. View

13.

Yano Y, Mitoma N, Ito H, Itami K . A Quest for Structurally Uniform Graphene Nanoribbons: Synthesis, Properties, and Applications. J Org Chem. 2019; 85(1):4-33. DOI: 10.1021/acs.joc.9b02814. View

14.

Gingras M . One hundred years of helicene chemistry. Part 3: applications and properties of carbohelicenes. Chem Soc Rev. 2012; 42(3):1051-95. DOI: 10.1039/c2cs35134j. View

15.

Rickhaus M, Jundt L, Mayor M . Determining Inversion Barriers in Atrop- isomers - A Tutorial for Organic Chemists. Chimia (Aarau). 2016; 70(3):192-202. DOI: 10.2533/chimia.2016.192. View

16.

Barroso J, Cabellos J, Pan S, Murillo F, Zarate X, Fernandez-Herrera M . Revisiting the racemization mechanism of helicenes. Chem Commun (Camb). 2017; 54(2):188-191. DOI: 10.1039/c7cc08191j. View

17.

Nakakuki Y, Hirose T, Matsuda K . Synthesis of a Helical Analogue of Kekulene: A Flexible π-Expanded Helicene with Large Helical Diameter Acting as a Soft Molecular Spring. J Am Chem Soc. 2018; 140(45):15461-15469. DOI: 10.1021/jacs.8b09825. View

18.

Kiel G, Patel S, Smith P, Levine D, Don Tilley T . Expanded Helicenes: A General Synthetic Strategy and Remarkable Supramolecular and Solid-State Behavior. J Am Chem Soc. 2017; 139(51):18456-18459. DOI: 10.1021/jacs.7b10902. View

19.

Zhang F, Michail E, Saal F, Krause A, Ravat P . Stereospecific Synthesis and Photophysical Properties of Propeller-Shaped C H PAH. Chemistry. 2019; 25(71):16241-16245. PMC: 6972628. DOI: 10.1002/chem.201904962. View

20.

Dhbaibi K, Favereau L, Crassous J . Enantioenriched Helicenes and Helicenoids Containing Main-Group Elements (B, Si, N, P). Chem Rev. 2019; 119(14):8846-8953. DOI: 10.1021/acs.chemrev.9b00033. View