Synthesis of Aza[n]helicenes (n = 4–7) via Photocyclodehydrochlorination of 1-Chloro-N-aryl-2-naphthamides

Abstract

A series of aza­[n]­helicenes (n = 4–7) was synthesized using a photocyclodehydrochlorination of 1-chloro-N-aryl-2-naphthamides as a general synthetic procedure introducing the nitrogen atom to the third ring of the helicene framework. The effect of the nitrogen presence in the helicene skeleton on the physicochemical properties of the prepared aza­[n]­helicenes was studied and compared to those of the parent carbo-analogues. The insertion of a nitrogen atom into the outer edge of the helicene molecule has a severe impact on certain physicochemical properties such as optical rotation, electrostatic potentials, and intermolecular interactions. On the other hand, some other properties such as UV/vis, fluorescence, and phosphorescence spectra remained almost unaffected when compared to the parent carbohelicenes. A nitrogen atom can be also used for further derivatization, which can lead to further modification of helicene properties, as manifested here in the fluorescence changes induced by protonation.

HFIP-promoted halo-carbocyclizations of N- and O-tethered arene–alkene substrates to access all halo (X = Br, I, Cl)-functionalized tetrahydroquinoline and chroman cores

“…Finally, on treatment with NBS in carbon tetrachloride solvent in the presence of light (unoptimized conditions) the compound 12 was fully aromatized to afford the 7-aza[5]helicene compound 13 in a good yield of 81% (Scheme 6b). 47 Based on our experimental observations and the previous literature, 33,44d we anticipated that HFIP plays an important role in this transformation and proposed a plausible reaction mechanism (Scheme 7). HFIP (i) causes strong hydrogenbonding as a non-covalent interaction between a carbonyl oxygen of NXS/DCDMH and the hydroxyl group of HFIP and helps to form in situ a three-membered haliranium ion intermediate.…”

“…Finally, on treatment with NBS in carbon tetrachloride solvent in the presence of light (unoptimized conditions) the compound 12 was fully aromatized to afford the 7-aza[5]helicene compound 13 in a good yield of 81% (Scheme 6b). 47…”

Ambient Temperature Dehydrogenative C(Ar)–H Carbonylative Lactamization of 2-Arylanilines Using DMF as C1-Source

“…These compounds could be achieved directly via 3a in gram scale by Sonogashira coupling. Compounds 2s – u and 2w are key intermediates for axial amino acids 6 and azahelicenes 7 which are functional optoelectronic materials for the OLED, CPPLED, and OFET (Scheme , bottom). , …”

“…Compounds 2s−u and 2w are key intermediates for axial amino acids 6 and azahelicenes 7 which are functional optoelectronic materials for the OLED, CPPLED, and OFET (Scheme 3, bottom). 13,14 The possible intermediate 8 could be easily afforded when 1a was treated by t BuOK in DMF without the irradiation of an LED (Scheme 4, eq 1). N-H deprotonation of 8 was observed by the 1 H NMR analysis, suggesting that the reaction might involve an amide anion intermediate (Supporting Information).…”