Azuacenes, defined as azulene fused with acenes in a 6-7-5 ring topology and spanning lengths from 3 to 6 rings, have been synthesized using a new skeleton editing and [3 + 2] annulation synthesis protocol as a distinction regarding the procedures to obtain the 6-5-7 isomers. Comprehensive studies on ground-state and excited-state spectroscopy, electrochemical properties, chemical stability, and solid-state structure have been conducted to compare these azuacenes with acenes. For the same number of rings, we found that azuacenes improve the chemical stability of acenes (i.e., smaller diradical character) and their photophysical properties (i.e., anti-Kasha emissions and modulation of the energy and strength of the visible bands) but they reduce the transport features compared to those of acenes. Compared with azulene, azuacenes improve the performance of azulene in terms of electrical properties. Overall, the fusion of known polycyclic compounds, such as acene and azulene, produces new isomeric hybrid compounds with enhanced properties. Here, the resulting compounds turn out to conserve most of the unique properties of the two building blocks that we associate with the facility of π-delocalization of the positive charge of the azulene zwitterion over the acene fragment.

This review covers articles published in the period from 2010 to mid-2022 on synthetic advances in the formation of pyrimidine and related heterocyclic compounds. Special emphasis has been given to the different types of cycloadditions, taking into account the number of their components and leading to the formation of the pyrimidine ring. Due to the large number of publications on the Biginelli reaction and related reactions, this will be dealt with in a separate review in the near future.

The relevance of the asymmetric Biginelli reaction (ABR) has been increased in this century, due to the pharmacological application of its products. This review focuses predominantly on articles published in the period from 2015 to 2024 on asymmetric synthetic advances in the formation of dihydropyrimidinones (DHPMs), dihydropyrimidinethiones (DHPMTs), and related compounds. The relevant bibliography on general processes in the Biginelli reaction and some methods of separation of isomers have also been referenced.

Three similar polycyclic aromatic hydrocarbon display outstanding emission properties, but only one displays amplified stimulated emission. The lack of available triplet states hinders the triplet formation allowing the amplified stimulated emission.

Sulfur-containing monosaccharide derivatives can be highly valuable for obtaining compounds with biological activities. In this work, a synthetic route starting from D-mannose has been designed. After a convenient hydroxyl protection and anomeric carbon functionalization in a cyano group, a new carbohydrate analogue has been obtained with sulfur in the ring. The heteroatoms have been introduced by an S_N2 mechanism, with subsequent cyclization. Structural identification has been performed by different spectroscopic techniques.

A series of molecules containing an oliquinane structural motif have been prepared. These oligoquinanes are constructed by connecting azulene units through the five-membered rings, resulting in a ladder-type structure of azulene oligomers. These oligoquinanes form a sequence of oligofulvene units which endow them with cross-conjugated character. In addition, through the 1-position of the central azulene unit, one carbazole is appended. A complete synthesis, solid-state studies, which document the formation of porous solids, and spectroscopic experimental characterization are carried out. The optical properties are analyzed as a function of the temperature in steady-state mode and by transient absorption. The whole study is guided and comprehensively rationalized by quantum chemical calculations. The hybridization of azulene and carbazole into an oligoquinane backbone confers the dual capacity of anti-Kasha fluorescence (azulene-like) and intersystem crossing (carbazole-like), enabling the synergistic emergence of anti-Kasha phosphorescence at 80 K. The observation of anti-Kasha phosphorescence is particularly notable, given that these are nearly pure hydrocarbons, i.e., heavy-atom-free organic chromophores. Furthermore, the design of new chromophores disclosing fluorescence and phosphorescence dual emissions in anti-Kasha mode is very appealing in organic photonics. In general, the discovery of modes of inferring additional properties to actuate from high energy lying excited states is of special interest in fields such as photochemistry, catalysis and photovoltaics.