Vladimir I. Sorokin

peri-Naphthylenediamines: 38. Naphthalene and acenaphthene proton sponges with +M substituents in ortho positions with respect to peri-dimethylamino groups

Previously unknown 4,5,6,7-tetrakis(dimethylamino)acenaphthene, which is the first acenaphthene derivative containing four vicinal dialkylamino groups, was synthesized based on 5,6-bis(dimethylamino)-4,7-dinitroacenaphthene. The total synthesis of 1,2,7,8-tetrakis(dimethylamino)naphthalene was carried out starting from 3,6-dinitronaphthalic anhydride. Other “proton sponges” of this type, viz., 1,7,8-tris(dimethylamino)-2-methoxy- and 1,8-bis(dimethylamino)-2,7-dipiperidinonaphthalenes, were prepared by the nucleophilic substitution in 2,7-dimethoxy-1,8-dinitronaphthalene. In solutions, 1,2,7,8-tetrakis(dimethylamino)naphthalene and its analogs can form di- and trications in the presence of acids. The basicity constants pKa1 of the compounds measured in DMSO depend in a complex way on their structures but correlate with the basicity index B, which is determined by changes in the chemical shifts δH after the addition of the first proton. Due to low C-nucleophilicity of ortho-disubstituted “proton sponges” in combination with high basicity, these compounds hold considerable promise as reagents in organic synthesis.

peri-Naphthylenediamines. 31. Study of interconversions of 2,3-dihydroperimidines and 1,8-bis(dialkylamino)naphthalenes. Convenient synthesis of 1,2,2,3-tetramethyl-2,3-dihydroperimidine and a monoisopropyl analog of the “proton sponge”

Efficient procedures were developed for the two-step synthesis of 1,2,2,3-tetramethyl-2,3-dihydroperimidines and for the one-step synthesis of 1,3-dimethyl-2,3-dihydroperimidines starting from 1,8-diaminonaphthalenes. New possibilities of the use of 2,3-dihydroperimidinium salts in the synthesis of 1,8-bis(dialkylamino)naphthalenes (“proton sponges”) containing the N-isopropyl group along with the N-methyl groups were demonstrated. The 1,1,2,2,3-pentamethyl-2,3-dihydroperimidinium cation exists in the acyclic iminium form responsible for its high reactivity.

peri-Naphthalenediamines: XXXIV. 1,4,5,8-Tetrakis(dimethylamino)naphthalene: Alternative Approaches to Synthesis

New methods were proposed for synthesizing 1,4,5,8-tetrakis(dimethylamino)naphthalene with an overall yield of 4 to 12% to replace the known procedure ensuring an overall yield of 2%. Catalytic hydrogenation was shown to be inapplicable for preparation of polyaminonaphthalenes from nitro compounds having 3 or 4 nitro gruops in the α-positions. Nucleophilic amination of 1,5-dinitronaphthalene in the system NH2OH/NaOH/MeOH yields 1-amino-4-nitronaphthalene. The nitration of 1,5-bis(p-tolylsulfonylamino)naphthalene leads to formation of 2,6-dinitro rather than 4,8-dinitro derivative, as it was believed formerly. This was confirmed by transformation of the latter into 1,2,5,6-tetrakis(dimethylamino)naphthalene. 3-Nitro, 2,6-dinitro, 2,6-diamino, and 2,4,6,8-tetranitro derivatives of 1,5-bis(dimethylamino)naphthalene, nitro and amino derivatives of 1,4,5-tris(dimethylamino)naphthalene, and 4,5-diamino-1,8-bis(methylamino)naphthalene were synthesized. By treatment with perchloric acid 1,4,5,8-tetrakis(dimethylamino)naphthalene was oxidized to 2,3-dihydroperimidinium salt.

Preparation of dialkylamino-substituted benzenes and naphthalenes by nucleophilic replacement of fluorine in the corresponding perfluoroaromatic compounds

The reactions between hexafluorobenzene (HFB) and octafluoronaphthalene (OFN) with secondary aliphatic amines (pyrrolidine, dimethylamine and piperidine) and lithium amides (pyrrolidide, dimethylamide and piperidide) have been investigated both experimentally and (in part) theoretically. With amines HFB, depending on the selected conditions, gives either di-substituted products or a complex mixture of di-, tri- and tetrasubstituted compounds. Under similar conditions OFN produces almost exclusively the 2,3,6,7-tetrasubstituted compound. Interaction of HFB with the more nucleophilic lithium amides results in the replacement of four fluorines giving 1,2,4,5-tetrasubstituted difluorobenzenes, while OFN under similar conditions with lithium pyrrolidide produces an inseparable mixture of 1,2,4,5,6,8-hexa- and 1,2,3,4,5,6,8-hepta-substituted derivatives. With lithium dimethylamide, it is possible to substitute six (in dioxane) or seven (in THF) fluorines in OFN. Lithium piperidide in all employed solvents reacts with OFN to give only the 1,2,4,5,6,8-hexasubstituted derivative. Theoretical calculations indicate that with lithium dimethylamide the third fluorine is substituted at position 1, whereas with dimethylamine it is position 3. The basicities of selected hexaand heptakis(dialkylamino)naphthalenes have been measured; they are all stronger bases than 1,8- bis(dimethylamino)naphthalene, although by less than expected.