Density Functional Theoretical Investigation on Influence of Heterosubstitution and Benzannelation on the Thermal 6π Electrocyclization of cis-Cyclononatetraene

Abstract

Thermal 6pi electrocyclization of cyclononatetraene (CNT), its hetero-substituted analogues, and its benzannelated derivatives have been investigated by using the B3LYP method employing 6-31G* and 6-311+G** basis sets. The results indicate that heterosubstitution and benzannelation influence the rate of cyclization. Nucleus independent chemical shifts (NICS), conceptual density functional theory (DFT) based reactivity descriptors, group electronegativity values, and barriers to planarity provide complementary evidence for the predicted rate of cyclization. The available experimental data are in good agreement with the computed values.

Cyclization of an α,β‐Unsaturated hydrazone catalyzed by a BINOL‐phosphoric acid: Pericyclic or not?

“…The computed reaction barrier for the cyclopentadienyl anion C is rather high. Literature values for DFT barriers of various pericyclic reactions cover a fairly large range and slightly depend on substituents and functionals . High‐level ab initio calculations predict a gas‐phase activation energy of 36–37 kcal/mol for C while B3LYP overestimates this value by about by 5–6 kcal/mol, which is in line with our present results (see Supporting Information Table 1, gas‐phase energy barrier of 42.7 kcal/mol for C ).…”

Reaction mechanisms : Part (ii) Pericyclic reactions

“…Elango and Subramanian used B3LYP calculations to explore the effects of heteroatom substitution (including groups containing B, C, O, N, F, Al, Si, S, P and Cl) and benzannelation (at several different positions) on the 6-electron electrocyclizations of cyclononatetraene (Chart 2). 19 Reaction and activation energies, enthalpies and free energies, NICS values, and chemical hardness and electrophilicity values were calculated and compared for these various reactions.…”

Prediction of a Nine−Membered Aromatic Heterocyclic 1,4,7−triazacyclononatetraenyl anion and its Sandwich Complexes with Divalent Lanthanides

“…The electronic and structural analogy of C 6 H 6 N 3 − with C 9 H 9 − ligand makes it attractive for the present study. It is important here to mention that 1,4,7−triaza−2,5,8−cyclononatriene C 6 H 6 (NR) 3 neutral ligand− with 6 π electrons and fully saturated 1,4,7−triazacyclononane− have been synthesized in the past. The metal complexes of 1,4,7−triazacyclononane ligand possess a wide range of applications, from catalysis to molecular imaging …”

“…− Although 1,4,7−triazacyclononane ligands are fully saturated however the unsaturated imino N can be introduced into the basic skeleton through photochemical reaction at ambient temperature condition . Moreover, various monohetero C 8 H 8 X analogue of C 9 H 9 − have been studied computationally, among which C 8 H 8 NH and C 8 H 8 N − are predicted to be aromatic . In the present work, we have investigated the aromatic behaviour of the newly proposed tacn ligand using its structural parameters, nucleus−independent chemical shift (NICS) and harmonic oscillator model of aromaticity (HOMA) values and compared with the corresponding values of its analogue C 9 H 9 − .…”