2,13-Diaza[5]helicene: synthesis, theoretical calculations and spectroscopic properties

Abstract

An easy approach to the synthesis of azahelicenes is based on the photochemical cyclisation of symmetrically or asymmetrically 1,2-aryl-substituted double bonds. In the synthesis of 2,13-diaza [5]helicene, irradiation of 9-(2-pyridin-4-yl-vinyl)-benzo[h]isoquinoline yielded 2,9-diazadibenzo[a.h]anthracene together with the desired helicene, and the ratio of the two products depends on the solvent. In this paper we suggest that the ratio between the two products should not be ascribed to different transitions induced by the solvent but to different populations of the two Z conformers

Helicity: A Non-Conventional Stereogenic Element for Designing Inherently Chiral Ionic Liquids for Electrochemical Enantiodifferentiation

“…We found rather difficult to separate 4 from racemic 1 by column chromatography on silica gel and minimize its formation by varying the reaction conditions. We attempted to perform photochemical ring closure of 3 in different solvents as previous investigations on a diazapentahelicene had evidenced how this step could be preferentially directed towards the formation of the azahelicene by the use of polar solvents [ 12 ]. However, in this case, the use of acetonitrile instead of ethyl acetate resulted in the almost exclusive formation of 4 , while using dichloromethane or toluene we obtained both products with a prevalence of 4 .…”

Enantioenriched Helicenes and Helicenoids Containing Main-Group Elements (B, Si, N, P)

“…91 Dehaen et al prepared racemic chloro-substituted diaza [5]helicene derivative 39 in 57% yield by oxidative photocyclization of stilbenic system 38 containing two 2-chloroquinoline units, in toluene for 10 h using iodine as the oxidant and then transformed 39 to (1:1) diastereomeric mixture 40a 1,2 in 72% Scheme 9. Synthesis of Mono-and Bis-aza- [5]helicenes Investigated by Oxidative Photocyclization, Except 35b 2 , Which Was Prepared by an Acid Cyclization Process 78,86,87 Chemical Reviews yield by a Buchwald−Hartwig coupling with enantiopure (S)-αmethylbenzylamine (Scheme 11). While trying to separate the diastereomers (P,S,S)-40a 1 and (M,S,S)-40a 2 by column chromatography at 10 °C, they found that these compounds were not configurationally stable, with half-life times t 1/2 of 26 min at 25 °C (ΔG # = 22.4 kcal mol −1 for racemization) and 4.2 h at 10 °C.…”

Tetrabenzo[b,de,gh,j][1,10]phenanthroline: a nitrogen-doped nanographene as a selective metal cation and proton fluorophore

“…1,10-Phenanthroline, one of the smallest N-doped graphene fragments, has exhibited remarkable coordination ability toward a wide range of metal cations, with further efficient and selective catalytic performance. 7 Its extended skeleton (including 7,8-diazabenzo[ ghi ]perylene, 8 core-doped tetraazaperopyrenes (c-TAPP) 9 and other N-doped graphene fragments 10 ) have been achieved (Scheme 1(a)). These molecules exhibit efficient photon propagating and/or sensitive mechanical force responses.…”