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

Abstract

The effect of peri‐fusion on the aromaticity of 6‐membered N−, O−, N,N−, N,N,N− and N,O‐doped naphthalene derivatives has been studied via NICS‐z, ‐xz, ‐xy, and ‐xyz scans employing DFT and MP2 calculations. The relative aromaticity of these structures was found to vary with the type of heteroring and the distance from the plane. Their corresponding ordering depends on the scan approaches. Accordingly, i) along the z axis at the center of the naphthalene B and C constituent rings, it is 1,8>2>7,9≫4>6, 5>3 (the most aromatic members are naphthalene and the N,O‐derivative 8), ii) along the x symmetry axis of naphthalene, it is 3>8,7>5>4>9>6>2>1 (the most aromatic one is a N‐derivative 3) and iii) along the z axis, on the xy plane, it is 6>1>8>9>2>5>7>3>4 at z=0.8 Å and 1>2>8>9>6>7>5>3>4 at 2.4 Å (the most aromatic ones are the N,N,N‐derivative 6 at 0.8 Å and naphthalene at 2.4 Å). Their relative magnetic anisotropy ordering remains virtually unaltered in all different approaches (z‐, xz‐, xy‐, and xyz‐scans), as does their aromaticity at z=2.4 Å. The σ component of the total density is dominant close to the plane while the π component picks up in significance with increasing distance from the plane. The peri‐fused ring appears to be a heteroring not just a heterobridge.

1H-Benzo[de]cinnolines: an interesting class of heterocycles

“…Dorofeenko et al demonstrated using 1 H NMR in CF3CO2H that 6-methoxy-1H-benzo[de]cinnoline 13 and its N-methyl derivative protonate on C7. 21 © ARKAT USA, Inc (10) with methyl and propyl iodides as well as with benzyl chloride in alkaline medium leads to the formation of the corresponding both N-substituted (11, 39, 40) and 9-substituted cinnoline derivatives (41,42) and also to the dimerization product (43) of the initial compound that corresponds to the formation of a N1-C9 bond (Scheme 3). 22 IR and 1 H NMR spectra were used to establish the structures; remember that protonation takes place at C7 while the alkylation occurs at C9.…”

“…39 Finally, there are two papers by Tsoungas et al in 2018 and 2021. 40,41 on the aromaticity of 1Hbenzo[de]cinnolines and related heterocycles based on NICS calculations, compound 1 being the most aromatic. 43 In the cited work of Tsoungas et al, 44 they analyzed the MEP to indicate that the reactivity of electrophiles towards 1 will occur at positions 3, 6 and 9, which is not the case.…”

The role of electric field, peripheral chains, and magnetic effects on significant 1H upfield shifts of the encapsulated molecules in chalcogen-bonded capsules

“…S23 of the ESI, † where a NICS-xyz scan has been carried out. Note that the NICS-scan identifies local and global ring currents in (poly)cyclic aromatic hydrocarbons and predicts their properties both qualitatively and quantitatively, see 32,33 and references therein. All A X +A X 0 cages, present unusually high magnetic anisotropy, see Fig.…”

A Powerful P−N Connection: Preparative Approaches, Reactivity, and Applications of P‐Stereogenic Aminophosphines

“…In addition, amino‐ and thiophosphates have recently been proposed as plausible molecules in early Earth scenarios [13] . Especially in the context of ligand design, oxidation of P(III) compounds with selenium has many advantages, as the 77 Se NMR spectroscopic parameters such as the 1 J P−Se coupling constant provide important information about the electronic nature of the new phosphines [7c,f,g] …”