For the first time, 10-dimethylamino derivatives of benzo[h]quinoline 6 and benzo[h]quinazoline 7a-e as mixed analogues of archetypal 1,8-bis(dimethylamino)naphthalene ("proton sponge") 1 and quino[7,8-h]quinoline 2a have been examined. Similar to 1 and 2, compounds 6 and 7 display rather high basicity, forming chelated monocations. At the same time, unexpected specifics of the protonated NMe2/-N═ systems consist of a strong shift of the NH proton to the 10-NMe2 group, contrary to the "aniline-pyridine" basicity rule. In case of 4H(+), a rapid migration (in the NMR time scale) of the NH proton between two nitrogen atoms along the N-H···N hydrogen bond was registered at room temperature and frozen below -30 °C with the proton fixed on the NMe2 group. Two different approaches for classification of strong neutral nitrogen organic bases as proton sponges (kinetically inert compounds) or pseudo-proton sponges (kinetically active) are discussed. On this basis, benzoquinoline 6 was identified as staying closer to pseudo-proton sponges while 7a-e to proton sponges due to the presence in their molecules of bulky substituents in the pyrimidine ring. Other remarkable peculiarities of 6 and 7 are their yellow color and luminescence in the visible region distinguishing them from colorless 1 and 2a.

It has been found that 2-bromo-1,8-bis(dimethylamino)naphthalene on sequential treatment with n-BuLi and 2 equiv of the same or different aryl(hetaryl) cyanide as a result of [2 + 2 + 2] nucleophilic cascade annulation produces 10-dimethylaminobenzo[h]quinazolines, as yet unknown NMe2/-N═ analogues of the proton sponge. It is even more convenient to use preliminarily prepared 2-ketimino-1,8-bis(dimethylamino)naphthalenes as starting material. The substitution of both peri-NMe2 groups furnishing quinazolino[7,8-h]quinazoline derivatives is also possible. The process is remarkable by surprisingly mild nucleophilic displacement of an unactivated aromatic NMe2 group.

The protonation of the carboxamide nitrogen atom is an essential part of in vivo and in vitro processes (cis‐trans isomerization, amides hydrolysis etc). This phenomenon is well studied in geometrically strongly distorted amides, although there is little data concerning the protonation of undistorted amides. In the latter case, the participation of amide nitrogen in hydrogen bonding (which can be regarded as the incipient state of a proton transfer process) is less well‐studied. Thus, it would be a worthy goal to investigate the enthalpy of this interaction. We prepared and investigated a set of peri‐substituted naphthalenes containing the protonated dimethylamino group next to the amide nitrogen atom (“amide proton sponges”), which could serve as models for the study of an intramolecular hydrogen bond with the amide nitrogen atom. X‐Ray analysis, NMR spectra, basicity values as well as quantum chemical calculations revealed the existence of a hydrogen bond with the amide nitrogen, that should be attributed to the borderline between moderate and weak intramolecular hydrogen bonds (2–7 kcal ⋅ mol−1).

Expanded quino-quinoline and quinazolino-quinazoline ligands change their emission upon protonation and π-coordination, model proton transfer and work in biphasic solvent systems.

A series of 2-ketimines and 2,7-diketimines of 1,8-bis(dimethylamino)naphthalene (proton sponge, DMAN) have been obtained and converted into the corresponding ketones via acidic hydrolysis. Investigation of structural and spectral properties of DMAN-based imines led to the conclusion that their unusual hydrolytic stability results from a combination of different factors the most important of which is a strong electron-donor effect of peri-dimethylamino groups.Imines are of common interest in organic synthesis, medicinal chemistry, and biochemistry. 1 However, in many cases handling imines, especially those with an unsubstituted NH group, is difficult due to the ease of their hydrolysis. Recently, we obtained two 2-ketimino derivatives of 1,8-bis(dimethylamino)naphthalene (1a, proton sponge, DMAN), namely 3a,b, and turned our attention to their enhanced hydrolytic stability. 2 To shed light on the origin of this phenomenon, in the present work we have prepared a number of new representatives of these compounds with widely varied structure and studied their properties (Scheme 1). In particular, we have focused on their hydrolytic activity, molecular structure, and mutual influence of the formally conjugated peri-NMe 2 and imino groups.Monoketimines 3a-f were synthesized in 60-89% yields by combining aryl and hetaryl cyanides with 1,8-bis(diamino)-1-lithionaphthalene (2, 2-Li-DMAN) generated from bromide 1b [Scheme 1 (a)]. 3 The reaction proceeded with more difficult for alkyl cyanides, apparently due to the enhanced acidity of their α-CH bonds causing protolysis of 2 [compare with the reactions of 2-lithium and 2,7-dilithium derivatives of 1,8-bis(dimethylamino)naphthalene with acetyl chloride 3 ]. Thus, on treatment of 2-Li-DMAN 2 with acetonitrile or valeronitrile the corresponding imines were not formed at all and only unsubstituted DMAN 1a was isolated from the reaction mixture. Use of tert-butyl cyanide, containing no α-CH bonds, was more successful and the yield of imine 3f reached 43%. Scheme 1To overcome this difficulty, we were forced to employ the reversed approach to synthesize alkyl(naphthyl)ketimines 3f-h by the interaction of ortho-cyanide 4 with alkyllithium reagents [Scheme 1 (b); notably the use of alkylmagnesium halides for this purpose failed]. To our satisfaction, imines with butyl and methyl groups 3g,h were obtained in good yields. Even for imine 3f containing the tert-butyl group the protocol increased the yield by 12% to 55%. Actually, both approaches were merged when 2-Li-DMAN 2 was allowed to react with nitrile 4 to produce symmetrical binaphthylketimine 3i (44%). Taking into account the higher nucleophilicity of 1,8-bis(dimethylamino)-2,7-dilithionaphthalene (6, 2,7-Li 2 -DMAN) in comparison with 2-Li-DMAN 2 and to confirm that two NMe 2 groups can stabilize two ortho-imino functionalities towards hydrolysis, it was also important to synthesize 2,7-diketimines of 1a. Interaction of 2,7-Li 2 -DMAN 6 with benzonitrile or 4-methoxybenzonitrile gave diimines 7a,b in 14% and 11% yields, respec...