Synthesis, conformational stability and molecular structure of 4-aryl- and 4, 5-diaryl-1, 8-bis(dimethylamino)naphthalenes. Issue 16 (3rd April 2023)

• Record Type: Journal Article
• Authors: Filatova, Ekaterina A.; Ermolenko, Eugeny A.; Pozharskii, Alexander F.; Ozeryanskii, Valery A.; Demidov, Oleg P.; Chernyshev, Anatoly V.; Metelitsa, Anatoly V.; Gulevskaya, Anna V.
• Is Part Of: Organic & biomolecular chemistry. Volume 21:Issue 16(2023)
• Page Start: 3388
• Page End: 3401
• Publication Date: 2023-04-03
• Subjects: Chemistry, Organic -- Periodicals; Bioorganic chemistry -- Periodicals; Chemistry, Physical organic -- Periodicals; 547
• DOI: 10.1039/d3ob00286a
• Languages: English
• ISSNs: 1477-0520

Abstract

Abstract : 4-Aryl- and 4, 5-diaryl-1, 8-bis(dimethylamino)naphthalenes were synthesized and comprehensively studied. Protonation leads to dramatic changes in their structures and properties. Abstract : 4-Bromo- and 4, 5-dibromo-1, 8-bis(dimethylamino)naphthalenes were arylated with arylboronic acids under Suzuki reaction conditions to provide 4-aryl- and 4, 5-diaryl-1, 8-bis(dimethylamino)naphthalenes, respectively. The interaction of 4, 5-dibromo-1, 8-bis(dimethylamino)naphthalene with pyridin-3-ylboronic acid was accompanied by heterocyclization leading unexpectedly to the formation of N 3, N 3, N 4, N 4 -tetramethylacenaphtho[1, 2- b ]pyridine-3, 4-diamine. Dynamic 1 H NMR experiments showed fast interconversion between syn and anti conformers of 4, 5-diaryl-1, 8-bis(dimethylamino)naphthalenes in CDCl3 solution at room temperature. The free energy of the rotational isomerization was determined to be ∼14.0 kcal mol −1 for 4, 5-di( m -tolyl) and 4, 5-di(naphthalen-2-yl) derivatives. X-ray analysis of 4, 5-diaryl-1, 8-bis(dimethylamino)naphthalenes revealed a high degree of structural deformation due to internal steric repulsions between both peri -dimethylamino and peri -aryl groups. In crystals, 4, 5-di(naphthalen-1-yl)-1, 8-bis(dimethylamino)naphthalene molecules exist exclusively in the most stable anti-out form, while for 4, 5-di(naphthalen-2-yl) and 4, 5-di( m -tolyl) counterparts, only the syn -form is realized. The introduction of two peri -aryl substituents in the 1, 8-bis(dimethylamino)naphthalene scaffold affected the basic properties, making the 4, 5-diphenyl derivative 0.7 p K a units less basic. The protonation of 4, 5-diaryl-1, 8-bis(dimethylamino)naphthalenes leads to dramatic changes in their structures. Compared to the corresponding bases, the inter-nitrogen distance in these salts noticeably decreases whereas peri -aromatic rings move away from each other demonstrating the so-called "clothespin effect". This lowers the barriers of syn / anti -isomerization; as a result, protonated molecules with peri-m -tolyl and even peri -(naphthalen-2-yl) substituents exist in crystals as mixtures of rotamers.