Synthesis of chiral spirodiazafluorenes
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Synthesis of chiral spirodiazafluorenes Yulia P. Ustimenko1, Eugene S. Vasilyev1*, Sergey N. Bizyaev1, Tatyana V. Rybalova1, Alexey V. Tkachev1 1
N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Branch of the Russian Academy of Sciences, 9 Akademika Lavrentieva Ave., Novosibirsk 630090, Russia; е-mail: [email protected] Submitted June 15, 2020 Accepted August 26, 2020
Translated from Khimiya Geterotsiklicheskikh Soedinenii, 2020, 56(11), 1429–1433
Reactions of chiral nopinane-annulated diazafluorenone with substituted phenols and naphthols by the action of trifluoromethanesulfonic acid led to spiro products. The structure of the resorcinol derivative was confirmed by X-ray structural analysis. Keywords: chiral bipyridyls, chiral pyridines, diazafluorenes, spiro compounds, terpenes, chirality, donor-acceptor systems, electrophilic alkylation.
π-Conjugated systems containing the fluorene fragment play an important role in organic electronics (organic lightemitting diodes,1a solar cells,1b storage devices1c) and can also form the skeleton of unusual aromatic systems.1d 4,5-Diazafluorene is a heterocyclic analog of fluorene and affords various possibilities for the coordination of metal ions.2 However, the possible wide range of applications of compounds in coordination chemistry and synthesis of polyaromatic systems containing the 4,5-diazafluorene fragment is limited by the low accessibility of 4,5-diazafluorene derivatives, for example, in comparison with the corresponding 1,10-phenanthrolines and 2,2'-bipyridyls. Previously, we proposed a method for the synthesis of diazafluorenone 13a annulated with nopinane and studied its reactions with a number of N-nucleophiles.3b Pyridines annulated with nopinane are convenient chiral objects that are widely studied in diastereoselective synthesis of coordination compounds, asymmetric catalysis, and supramolecular design.4 Unsubstituted diazafluorenone is known to undergo a reaction with phenols and naphthols in a stoichiometric ratio of 1:2 catalyzed by trifluoromethanesulfonic acid with the formation of spiro products containing the xanthene and diazafluorene fragments.5 The mechanism of this reaction is a cascade of cationoid transformations.5 This method makes it possible to design aromatic donor-acceptor spiro systems, which are widely studied due to the possibility of photoinduced electron transfer and other unusual physicochemical properties.6 0009-3122/20/56(11)-1429©2020 Springer Science+Business Media, LLC
Spiroxanthene systems are of great interest as a special case of donor-acceptor spiro systems.7 In this work, chiral diazafluorenone 1 was reacted with an excess of phenol or naphthol in the presence of an excess of trifluoromethanesulfonic acid and p-chlorobromobenzene as a solvent. In this case, spirocyclic products with a stoichiometry of 1:2 were obtained (Scheme 1). The best yields of the spirocyclization reaction were obtained in the case of 1-naphthol (90%) and resorcinol (71%). In the case of hydroquinone, the product was formed in go
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