Synlett 2016; 27(04): 498-525
DOI: 10.1055/s-0035-1560524
account
© Georg Thieme Verlag Stuttgart · New York

Synthesis of Heterocyclic [8]Circulenes and Related Structures

Thomas Hensel, Nicolaj N. Andersen, Malene Plesner, Michael Pittelkow*
  • Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark   Email: pittel@kiku.dk
Further Information

Publication History

Received: 09 August 2015

Accepted after revision: 29 September 2015

Publication Date:
22 December 2015 (eFirst)

Abstract

In this account we give an overview of the synthesis and properties of heterocyclic [8]circulenes. Much of the interest in studying heterocyclic [8]circulenes stems from the planar cyclooctatetraene core often contained in these compounds, which in principle is antiaromatic. We start with a short introduction to the hydrocarbon [n]circulenes and proceed to describe the synthetic chemistry involved in creating tetraoxa[8]circulenes, with particular focus on the acid-mediated oligomerization of benzo- or naphthoquinones, resulting in some simple rules for predicting the outcome of the oligomerization reactions. These rules have guided the synthetic strategies for the preparation of azatrioxa[8]circulenes and diazadioxa[8]circulenes, which will be described in separate sections of this account. More traditional synthetic strategies have been applied in the preparation of octathia[8]circulene, tetrathiatetraselena[8]circulene, and a number of other heterocyclic [8]circulenes, and these synthetic efforts will be highlighted. Finally, a section describing structures that are closely related to the heterocyclic [8]circulenes will be presented, and at the end we will comment on the extensive theoretical work regarding the question of aromaticity/anti­aromaticity of the central cyclooctatetraene of heterocyclic[8]circulenes.

1 Introduction

2 Synthesis of [n]circulenes

2.1 [4]Circulene

2.2 [5]Circulene

2.3 [6]Circulene

2.4 [7]Circulene

2.5 [8]Circulene

3 Synthesis of Tetraoxa[8]circulenes: A Historical Perspective

4 Synthesis of Azatrioxa[8]circulenes

5 Synthesis of Diazadioxa[8]circulenes

6 Synthesis of Other Heterocyclic [8]Circulenes

7 Synthesis of Structurally Related Compounds

8 Hetero[8]circulenes and Related Compounds as Tools to Study Aromaticity and Antiaromaticity

9 Conclusion and Outlook