Synthesis and Derivatization of N-Heterotriangulenes (Microreview)
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Synthesis and derivatization of N-heterotriangulenes (microreview) Jana Petkus1, Kirill Shubin1* 1
Latvian Institute of Organic Synthesis, 21 Aizkraukles St., Riga LV-1006, Latvia; е-mail: [email protected] Submitted May 6, 2020 Accepted May 17, 2020
Published in Khimiya Geterotsiklicheskikh Soedinenii, 2020, 56(5), 512–514
A summary of the known approaches toward the synthesis of N-heterotriangulenes is presented. The microreview contains various types of organic reactions for the synthesis and one-step modification of the N-heterotriangulene core. The review covers recent data that was not included into other review articles.
Introduction Substituted N-heterotriangulenes are used for the preparation of dye-sensitized solar cells1,2 and as donor–π-bridge–acceptor photosensitizers3. They show big potential in the design of new nanomaterials and organic light-emitting devices (OLEDs).4,5
Recently, many aspects of N-heterotriangulene chemistry were summarized in two reviews by Schaub et al.6 and Hirai et al.7 Present microreview focuses on the examples that were not included into the previous reviews.
Friedel–Crafts cyclization The first synthesis of triketone N-heterotriangulene 6 (with 37% yield) was described by Hellwinkel and Melan in 1971,8 and later improved by Field and Venkataraman (80% yield of triketone 6).9 Their four-step synthesis started from the preparation of triester 3 by refluxing methyl anthranilate (1) and metyl 2-iodobenzoate (2) in o-dichlorobenzene in the presence of a base (K2CO3) and catalysts (powdered Cu
and 18-crown-6 ether). Van der Heijden et al. synthesized the same heterotriangulene 6 via triester 3 in two-step procedure under different conditions.10 Triester 3 was directly cyclized to compound 6 with H2SO4, however, with a very low yield (only 7%). Symmetrically 2,6,10-trisubstituted triangulenes (including trihalogenated) can be prepared by the same method from appropriately substituted triesters.11,12
Kirill Shubin was born in 1976 in Saint Petersburg, Russia. He graduated from the SaintPetersburg State Institute of Technology in 2000 and obtained his PhD in chemistry at the same Institute. At present he is a research group leader at the Latvian Institute of Organic Synthesis. His scientific interests include metal-organic compounds, diastereoselective synthesis, and synthesis of natural compounds.
Jana Petkus was born in 1996 in Jurmala, Latvia. She obtained BSc degree from the University of Latvia in 2018 and currently continues her MSc studies in the group of Dr. K. Shubin at the Latvian Institute of Organic Synthesis. Her research interests include metal-organic chemistry, transition metal-catalyzed cross-coupling reactions.
0009-3122/20/56(5)-0512©2020 Springer Science+Business Media, LLC
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Chemistry of Heterocyclic Compounds 2020, 56(5), 512–514
Cyclization of tertiary alcohols A method for the preparation of hexamethyl-substituted triangulene 8 was developed by Fang et al.13 Grignard reagent is used to convert triester 3 to triol 7, and then the triol is cyclized in
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