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A systematic study of the synthesis and properties of 1‐aza‐, 4‐aza‐, and 1,4‐diaza[4]helicenes as well as the previously unknown S‐shaped double 1,4‐diaza[4]helicenes has been reported. The synthetic route to the aza‐ and diaza[4]helicenes involved an electrophile‐induced cyclization of 3(2)‐alkynyl‐2(3)‐(naphthalen‐1‐yl)azines (i.e., quinoxaline, pyrazine, pyridine), which were prepared in two steps from the commercially available ortho‐dihalo‐substituted azine. Trifluoroacetic acid (TFA) and ICl were used as electrophiles. The ICl‐promoted cyclization provided the 5‐iodo derivatives of the aza‐ and diaza[4]helicenes in yields of 47–71 %. The use of TFA as the electrophile afforded the helicenes along with isomeric products from an alternative cyclization and subsequent 1,2‐shift of the C–C bond (e.g., naphtho[2,1‐f]quinoxalines or naphtho[2,1‐a]phenazines, 87–89 % total yield, 1.5–1.8:1 ratio). The presence of an iodine substituent in the hetero[4]helicenes allowed for the introduction of an alkynyl group by using a Sonogashira reaction. The subsequent cycloizomerization upon treatment with TFA gave the S‐shaped double 1,4‐diaza[4]helicenes. The molecular structures and crystal packing of the synthesized hetero[4]helicenes relative to those of [4]carbohelicene have been discussed.

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A new family of arylene‐ethynylene oligomers consisting of two, three and four “proton sponge” fragments (1,8‐bis(dimethylamino)naphthalene or DMAN) alternating with C≡C bonds were synthesized using various 2‐ and 4‐ethynyl and 2‐ and 4‐iodo derivatives of DMAN as synthetic building blocks in the Sonogashira coupling. X‐ray structural, photophysical, chemical and electrochemical properties showed that the oligomers are promising candidates to construct materials with varied rigidity (tuned by protonation), electron conductivity (tuned by mode of linkage), and proton conductivity (equilibration of protonated and free DMAN subunits).

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A facile synthesis of benzo[a]‐, naphtho[1,2‐a]‐ and naphtho[2,1‐a]phenazines by ICl‐promoted 6‐endo‐dig cyclization of 3‐alkynyl‐2‐arylquinoxalines has been developed. The starting 3‐alkynyl‐2‐arylquinoxalines were synthesized from 2,3‐dichloroquinoxaline by two successive Sonogashira and Suzuki–Miyaura reactions. The method works well for 3‐alkynyl‐2‐arylquinoxalines bearing various functional groups at the alkyne moiety. The arrangement and nature of the substituent in the 2‐aryl fragment affect the regioselectivity of the cyclization. For the substrate of one particular type, namely 2‐(4‐methoxyphenyl)‐3‐(p‐tolylethynyl)quinoxaline, the treatment with ICl leads to the alternative 5‐endo‐dig cyclization followed by demethylation of the methoxy group to give a spirocyclohexadienone derivative.

Suzuki arylation of 2‐halogeno and 2,7‐dihalogeno derivatives of 1,8‐bis(dimethylamino)naphthalene (proton sponge) was carried out. It was shown that the sterically hindered nature of the starting compounds in combination with the enhanced reactivity of their peri‐NMe2 groups allow to obtain the target 2‐aryl and 2,7‐diaryl derivatives in 20–34 % yields only. In most cases, a tandem Pd‐catalyzed hydrodehalogenation/N‐demethylation process was predominant. The latter, however, makes it possible to obtain yet unknown and synthetically valuable 2‐aryl‐N1,N1,N8‐trimethyl‐1,8‐diaminonaphthalenes (21–50 %), which can be easily converted into the corresponding proton sponges by conventional N‐methylation. Using the literature data on 2,7‐disubstituted derivatives of the proton sponge as a background together with the XRD and basicity measurements performed in this work, a comprehensive analysis of the so‐called “buttressing effect” in 2‐aryl‐ and 2,7‐diaryl‐1,8‐bis(dimethylamino)naphthalenes, along with previously unknown 2,6‐diphenyl‐N,N‐dimethyl‐p‐toluidine has been carried out for the first time.

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