Synthesis of π-conjugated polycyclic compounds by late-stage extrusion of chalcogen fragments

• Aissam Okba,
• Pablo Simón Marqués,
• Kyohei Matsuo,
• Naoki Aratani,
• Hiroko Yamada,
• Gwénaël Rapenne and
• Claire Kammerer

Beilstein J. Org. Chem. 2024, 20, 287–305, doi:10.3762/bjoc.20.30

• , this class of compounds is prone to valence isomerization via 6π-electrocyclization leading to the formation of heteroatom-containing norcaradiene, and oxepine has been shown to exist in equilibrium with its valence isomer benzene oxide [37]. In contrast with the parent oxepine, which is isolable at

• design of pentacene’s soluble precursor, as reported by Müllen and Herwig [14], is depicted in the top left. Valence isomerization of chalcogen heteropines and subsequent cheletropic extrusion in the case of sulfur, selenium and tellurium derivatives. Early example of phenanthrene synthesis via a

Selected synthetic strategies to cyclophanes

• Sambasivarao Kotha,
• Mukesh E. Shirbhate and
• Gopalkrushna T. Waghule

Beilstein J. Org. Chem. 2015, 11, 1274–1331, doi:10.3762/bjoc.11.142

3-Pyridylnitrene, 2- and 4-pyrimidinylcarbenes, 3-quinolylnitrenes, and 4-quinazolinylcarbenes. Interconversion, ring expansion to diazacycloheptatetraenes, ring opening to nitrile ylides, and ring contraction to cyanopyrroles and cyanoindoles

• Curt Wentrup,
• Nguyen Mong Lan,
• Adelheid Lukosch,
• Pawel Bednarek and
• David Kvaskoff

Beilstein J. Org. Chem. 2013, 9, 743–753, doi:10.3762/bjoc.9.84

• and Figure 1). 2- and 4-pyrimidinylcarbenes FVT of tetrazolylpyrimidines of type 19 causes elimination of N2 to generate 4- and 2-diazomethylpyrimidines 20, which can ring-close to the corresponding 1,2,3-triazolopyrimidines 21 (Scheme 7) [23]. Endothermic ring-chain valence isomerization of the type

Valence isomerization of cyclohepta-1,3,5-triene and its heteroelement analogues

• Helen Jansen,
• J. Chris Slootweg and
• Koop Lammertsma

Beilstein J. Org. Chem. 2011, 7, 1713–1721, doi:10.3762/bjoc.7.201

• Helen Jansen J. Chris Slootweg Koop Lammertsma Department of Chemistry and Pharmaceutical Sciences, VU University Amsterdam, De Boelelaan 1083, 1081 HV, Amsterdam, The Netherlands 10.3762/bjoc.7.201 Abstract The valence isomerization of the all-carbon and heteroelement analogues of cyclohepta

• -1,3,5-triene into the corresponding bicyclo[4.1.0]hepta-2,4-dienes is reviewed to show the impact of the heteroatom on the stability of both valence isomers. The focus is on the parent systems and their synthetic applications. Keywords: aromaticity; cycloheptatriene; heteroatom; valence isomerization

• ; Introduction The valence isomerization of cyclohepta-1,3,5-triene (1) into bicyclo[4.1.0]hepta-2,4-diene (2) has captured the attention of chemists for over five decades [1][2]. This interest extended to the heterocyclic analogues 3–8, bearing one oxygen, sulfur or nitrogen atom, after the discovery of their