Substitution reactions in the acenaphthene analog of quino[7,8-h]quinoline and an unusual synthesis of the corresponding acenaphthylenes by tele-elimination

The possibility of functionalization of dipyrido[3,2-e:2′,3′-h]acenaphthene containing a quino[7,8-h]quinoline fragment and being a highly basic diazine analog of 1,8-bis(dimethylamino)naphthalene (“proton sponge”) has been studied for the first time. In addition to the pronounced tendency of the title compound to form associates with an intramolecular hydrogen bond of the NHN type (new examples with the participation of pyridine rings, including self-associates are shown) and its inertness to amination reactions of the pyridine rings, the naphthalene core at positions 5(8) and the CH2CH2 bridge (dehydrogenation) undergo chemical modifications under mild conditions, giving the corresponding acenaphthylenes. The latter can also be obtained in an unusual way by tele-elimination from 5,8-dibromodipyridoacenaphthene by reaction with neutral or anionic bases

SNH Amidation of 5-Nitroisoquinoline: Access to Nitro- and Nitroso Derivatives of Amides and Ureas on the Basis of Isoquinoline

For the first time, amides and ureas based on both 5-nitroisoquinoline and 5-nitrosoisoquinoline were obtained by direct nucleophilic substitution of hydrogen in the 5-nitroisoquinoline molecule. In the case of urea and monosubstituted ureas, only 5-nitrosoisoquinoline-6-amine is formed under anhydrous conditions

Divergent Transformations of 2‑Nitro‑1<i>H</i>‑benzo[<i>f</i>]chromenes in Reactions with Alkylidenemalononitriles: Access to Naphtho[2,1‑<i>b</i>]furans via Base-Mediated Pyran Ring Contraction

The action of 2-(1-arylethylidene)malononitriles on 2-nitro-1H-benzo[f]chromenes in the presence of Et3N and MoO3·2H2O results in naphtho[2,1-b]furans containing an allylidenemalononitrile unit in the α-position. The reaction proceeds with contraction of the pyran ring via a cascade carba-Michael addition/retro-oxa-Michael reaction/tautomerization/SN2/oxidation process. In contrast, the reaction of 2-nitro-1H-benzo[f]chromenes with the cyclic Knoevenagel adduct derived from 1-indanone and malononitrile leads to dihydroindeno[1,2-c]xanthenes. The possibility of further transformations of naphtho[2,1-b]furan derivatives as useful precursors and their optical properties were also investigated

Organometallic Synthesis of 2,3,6,7-Tetrasubstituted 1,8-Bis(dimethylamino)naphthalenes for Investigation of the Double Buttressing Effect in Proton Sponges

The lithiation of 2,7-disubstituted derivatives of 1,8-bis(dimethylamino)naphthalene (DMAN, proton sponge) bearing potentially ortho-directing OMe, NMe2, and SMe groups was studied. It has been shown that OMe groups facilitate selective dual β-lithiation of the naphthalene moiety while the 2(7)-NMe2 groups allow only monolithiation presumably due to the decreased acidity of the ring C–H bonds and conformational immobilization after coordination to the lithium atom. In contrast, the SMe groups provided no ring lithiation and underwent deprotonation of their methyl fragment. The first representatives of previously unknown 2,3,6,7-tetrasubstituted DMANs have been synthesized in good yield after treatment of 2,7-dimethoxy-3,6-dilithio DMAN with the appropriate electrophiles (MeI, Me2S2, Me3SiCl, DMF, etc.). Because the exceedingly high basicity of 2,7-dimethoxy DMAN is commonly attributed to the so-called “buttressing effect” (BE), the availability of 2,3,6,7-tetrasubstituted species provided the first opportunity to study the double BE version. Using X-ray diffraction and basicity measurements, we showed that due to the high conformational mobility of the methoxy groups, the most striking manifestations of double BE are the strong planarization of peri-NMe2 groups and a significant decrease in basicity, while the length and the other properties of the intramolecular NHN hydrogen bond in the corresponding protonated species undergo minor changes

Organometallic Synthesis of 2,3,6,7-Tetrasubstituted 1,8-Bis(dimethylamino)naphthalenes for Investigation of the Double Buttressing Effect in Proton Sponges

The lithiation of 2,7-disubstituted derivatives of 1,8-bis(dimethylamino)naphthalene (DMAN, proton sponge) bearing potentially ortho-directing OMe, NMe2, and SMe groups was studied. It has been shown that OMe groups facilitate selective dual β-lithiation of the naphthalene moiety while the 2(7)-NMe2 groups allow only monolithiation presumably due to the decreased acidity of the ring C–H bonds and conformational immobilization after coordination to the lithium atom. In contrast, the SMe groups provided no ring lithiation and underwent deprotonation of their methyl fragment. The first representatives of previously unknown 2,3,6,7-tetrasubstituted DMANs have been synthesized in good yield after treatment of 2,7-dimethoxy-3,6-dilithio DMAN with the appropriate electrophiles (MeI, Me2S2, Me3SiCl, DMF, etc.). Because the exceedingly high basicity of 2,7-dimethoxy DMAN is commonly attributed to the so-called “buttressing effect” (BE), the availability of 2,3,6,7-tetrasubstituted species provided the first opportunity to study the double BE version. Using X-ray diffraction and basicity measurements, we showed that due to the high conformational mobility of the methoxy groups, the most striking manifestations of double BE are the strong planarization of peri-NMe2 groups and a significant decrease in basicity, while the length and the other properties of the intramolecular NHN hydrogen bond in the corresponding protonated species undergo minor changes