Aromaticity in the Light of Magnetic Criteria

The origin of experimental regioselectivity in ring-closing reaction of pyrido[1,2-e]purine systems and comparison of the aromaticity character of probable products: a mechanistic study based on DFT insights

“…1 Aromaticity as a fundamental concept is linked to a variety of different molecular properties, including stability, molecular system planarity, conjugation, electron delocalization, and a distinctive reactivity to an external magnetic field. [2][3][4][5] Based on energetic criteria of aromaticity, the aromatic compounds are more stable than their counterparts with localized double and single bonds. Also, they have an electron ring current induced in a magnetic field.…”

“…6 In modern times, the concept of aromaticity encompasses all metal aromatic clusters in addition to aromaticity has gathered a growing amount of interest. [27][28][29] It should be mentioned in this regard that Alkorta and his colleagues recently published the physical characteristics of linear, angular [1,2,3]triazoloquinazoline isomers. The result that bent isomers are considerably more stable than linear ones agrees with all known experimental data.…”

“…Shiri and coworkers reported the synthesis of 3-alkyl-pyrido [1,2-e] [1,2,4]triazolo [4,3-a]purines (3-H, 3-Me and 3-Et) by 2-chloro-4-methylpyrido[1,2-e]purine (1) via a nucleophilic aromatic substitution (S N Ar) amination mechanism. 31 The treatment of (1) with hydrazine hydrate led to 2-hydrazinyl-4-methylpyrido[1,2-e]purine (2), and after that, the reaction between (2) and three triethyl orthoesters (RC(OEt) 3 )s was promoted to give three derivatives of heterocyclic compounds (3) as two regioisomers of 3-H, 3-Me and 3-Et substituents (Scheme 1). They reported that the ring-closing in the presence of triethyl orthoesters goes through a regioselective cyclization reaction.…”

N,N‐ and N,O‐6‐membered Ring peri‐Annelation in Naphthalene. Is it a Heteroring or merely a peri‐ Heterobridge?

“…Condensed (or fused) polycyclic (hetero) aromatic compounds (P(H)ACs) have also shared an extensive research interest, thanks to their intriguing geometry features [5–7] and diverse applications [8–11] . In trying to quantify, thus, give a physical substance to the concept, various indices/ descriptors have been developed over the years, such as structural, [12,13] magnetic, [7,14,15] energetic, [13] electronic [16] and reactivity‐based ones, [17] to measure the degree of aromaticity of PAHs and their heterocyclic analogues [2,15,18–22] . A succinct presentation [23] and assessments [18–26] of these indices have been reported.…”

Vorticity: Simplifying the analysis of the current density

“…It can also be used to study the electron delocalization in bonds and molecules . Moreover, this vector field has been extensively used to study and evaluate one of the most important concepts in chemistry, the aromaticity . This concept is not a physical observable, therefore, several indices based in the geometric, energetic, electronic, and magnetic properties have been proposed to evaluate it .…”