Is planarity of pyridin-2-yl- and pyrazin-2-yl-formamide thiosemicarbazones related to their tuberculostatic activity?

Abstract

Structures of 8-dimethylamino-1-methylamino-4-nitronaphthalene (1), 1-dimethylamino-8-methylamino-4-nitronaphthalene (2), 1-dimethylamino-2,7-dimethoxy-8-methylamino3,5-dinitronaphthalene (3) and 1,2,4-tribromo-6-dimethylamino-5-methylaminoacenaphthylene (4) were studied for the first time [1,2]. The remarkable importance of intramolecular hydrogen bonds (IHB) has long been recognized in the chemistry of 1,8-bis(dimethylamino)naphthalene (’’proton sponge’’) and its numerous analogues [3]. It was shown that the formation of IHB in proton sponges is responsible for the unusually high basicity of this compound (pKa=12.1, H2O, 25(C) [4]. Symmetry and low-barrier character of the N ...H ...N bond in proton sponges attract considerable attention from the standpoint of theory modeling proton transfer processes in biological systems [5]. In this respect, structural parameters of hydrogen bridge in 1,8-diaminonaphthalenes are intriguing to study. Correlations between basicity of ’’proton sponges’’ (1-4), IHB parameters and other geometric characteristics of themolecules will be discussed.