E. V. Kondrashov

Fragmentation of Trifluoromethylated Alkenes and Acetylenes by N,N-Binucleophiles. Synthesis of Imidazolines or Imidazolidines (Oxazolidines) Controlled by Substituent

The reaction of beta-halogeno-beta-polyfluoromethylstyrenes with N,N- or N,O-binucleophiles leads to unexpected fragmentation products (imidazolines) or to heterocyclization giving CF(3)-substituted imidazolidines (N,N-) and oxazolidines (N,O-) depending on aryl substituent. The scope and the reaction mechanism are discussed.

GIAO, DFT, AIM and NBO analysis of the NH···O intramolecular hydrogen‐bond influence on the 1J(N,H) coupling constant in push–pull diaminoenones

In the series of diaminoenones, large high‐frequency shifts of the 1H NMR of the NH group in the cis‐position relative to the carbonyl group suggests strong NH···O intramolecular hydrogen bonding comprising a six‐membered chelate ring. The NH···O hydrogen bond causes an increase of the 1J(N,H) coupling constant by 2–4 Hz and high‐frequency shift of the 15N signal by 9–10 ppm despite of the lengthening of the relevant NH bond. These experimental trends are substantiated by gauge‐independent atomic orbital and density functional theory calculations of the shielding and coupling constants in the 3,3‐bis(isopropylamino)‐1‐(aryl)prop‐2‐en‐1‐one (12) for conformations with the Z‐ and E‐orientations of the carbonyl group relative to the NH group. The effects of the NH···O hydrogen‐bond on the NMR parameters are analyzed with the atoms‐in‐molecules (AIM) and natural bond orbital (NBO) methods. The AIM method indicates a weakening of the NH···O hydrogen bond as compared with that of 1,1‐di(pyrrol‐2‐yl)‐2‐formylethene (13) where NH···O hydrogen bridge establishes a seven‐membered chelate ring, and the corresponding 1J(N,H) coupling constant decreases. The NBO method reveals that the LP(O) →σ*NH hyperconjugative interaction is weakened on going from the six‐membered chelate ring to the seven‐membered one due to a more bent hydrogen bond in the former case. A dominating effect of the NH bond rehybridization, owing to an electrostatic term in the hydrogen bonding, seems to provide an increase of the 1J(N,H) value as a consequence of the NH···O hydrogen bonding in the studied diaminoenones. Copyright

Selective, Metal-Free Approach to 3- or 5-CF3-Pyrazoles: Solvent Switchable Reaction of CF3-Ynones with Hydrazines

A detailed study of the reaction of trifluoroacetylated acetylenes and aryl (alkyl) hydrazines was performed, aimed to the regioselective synthesis of 3- or 5-trifluoromethylated pyrazoles. It was found that the regioselectivity of reaction depends dramatically on the solvent nature. Highly polar protic solvents (hexafluoroisopropanol) favor the formation of 3-trifluoromethylpyrazoles. In contrast, when the reaction was performed in polar aprotic solvents (DMSO), the formation of their 5-CF3-substituted isomers was preferentially observed. Alternatively, the regioselective assembly of 3-CF3-substituted pyrazoles can be performed via two-step one-pot procedure. The reaction of trifluoromethylated ynones with aryl (alkyl) hydrazines in the presence of acidic catalysts leads to formation of the corresponding hydrazones. The latter can be smoothly transformed into 3-CF3-pyrazoles by treatment with a base. This solvent-switchable procedure was used for the preparation of such important drugs as Celebrex and SC-560 as well as their isomers in gram scale. The possible reaction mechanism is discussed.

Reactions of N-(Polychloroethylidene)arene-and - trifluoromethanesulfonamides with indoles

N-(Polychloroethylidene)arene-and -trifluoromethanesulfonamides reacted with indole and N-substituted indoles to give the corresponding N-[2,2-dichloro(or 2,2,2-trichloro)-1-(1H-indol-3-yl)ethyl]-substituted sulfonamides. Unlike N-(2,2,2-trichloroethylidene)trifluoromethanesulfonamide, less electrophilic N-(poly-chloroethylidene)arenesulfonamides failed to react with 1-(4-nitrophenyl)-1H-indole. Previously unknown N,N’-bis(2,2-dichloroethylidene)biphenyl-4,4’-disulfonamide reacted with 1-benzyl-1H-indole at both azomethine fragments. Likewise, reactions of 1,6-bis(1H-indol-1-yl)hexane and 1,4-bis(1H-indol-1-ylmethyl)-benzene with N-sulfonyl trichloroacetaldehyde imines involved both indole rings in the former.

Synthesis and Properties of N-(2,2,2-Trichloroethylidene)trifluoromethanesulfonamide and Its Derivatives

The reaction of N,N-dichloromethanesulfonamide with trichloroethylene gave N-(2,2,2-trichloro- ethylidene)trifluoromethanesulfonamide which showed high reactivity toward oxygen- and nitrogen-centered nucleophiles, as well as in C-alkylation of aromatic compounds.

Unexpected reaction of dibenzyl disulfide with hydrazine

The reaction of hydrazine with dichalcogenides in aqueous alkaline medium is known to result in reductive cleavage of dichalcogenides giving thiols [1] and other chalcogenols [2], and hydrazine therewith is oxidized into nitrogen. We found that the reaction of dibenzyl disulfide with excess hydrazine hydrochloride in DMF in the presence of sodium or potassium carbonates at heating to 100°C unexpectedly afforded benzalazine. The process was accompanied by hydrogen sulfide evolution. It is presumable that under the conditions of the reaction the dibenzyl disulfide suffered 1,2-elimination with the formation of benzylthiol and thiobenzaldehyde. The latter underwent condensation with hydrazine to give the final benzalazine that apparently existed in the reaction mixture as thioaminal or hemiaminal, but was isolated at acidifying the reaction mixture in the individual state in 38% indicating a good yield of the intermediate thioaldehyde.

Synthesis and structure of 4-trifluoromethylsulfonamidotrichloroethyl-5-chloropyrazoles

Reactions of trifluoromethanesulfonic acid N-(2,2,2-trichloroethylidene)amide with 1,3-dialkyl-5-chloropyrazoles and 1-phenyl-3-methylpyrazole afforded 4-(amidotrichloroethyl)-substituted pyrazole derivatives. 4-Chloropyrazoles were not involved into this process. The structure of compounds synthesized was studied by means of IR and NMR spectroscopy. The presence of intra- and intermolecular hydrogen bonds was revealed by a decrease in the absorption frequencies and a complicated form of ν(NH) and νas(SO2) absorption bands in the IR spectra, and also in splitting of signals in 1H and 13C NMR spectra.

Synthesis and reactions of 1-benzyl-3-haloalkyl-5-chloropyrazoles

Synthesized 1-benzyl-3-chloroalkyl-5-chloropyrazoles reacted with indole and pyrrole in DMSO in the presence of alkali to give 3-(heter-1-yl)alkyl-substituted 1-benzyl-5-chloropyrazoles. 1-[(1-Benzyl-5-chloropyrazol-3-yl)methyl]indole reacted regiospecifically with chloroal trifluoromethylsulfonyl- and 4-chlorophenylsulfonylimines providing the products of C-amidotrichloroethylation into the position 3 of the indole ring. {1-[(1-Benzyl-5-chloropyrazol-3-yl)methyl]indol-3-yl}sulfanylacetic acid was obtained by the reaction of 1-[(1-benzyl-5-chloropyrazol-3-yl)methyl]-indole with iodine, thiourea, and chloroacetic acid.

Reaction of N,N-dichlorosulfonamides with tribromoethylene

Reaction of aryl-and trifluoromethanesulfonic acids N,N-dichloroamides with tribromoethylene led to the formation of a mixture of N-(2,2-dibromo-2-chloroethylidene)-and N-(2,2,2-tribromoethylidene)amides of the corresponding sulfonic acids. The azomethines ratio is governed by the reaction temperature.

Alkyl-and arylsulfanyl-substituted unsaturated carbonyl compounds

ABSTRACT A method for the synthesis of captodative sulfanyl enals, enones and enoates via nucleophilic vinylic substitution of corresponding halogen-bearing derivatives has been developed. The one-pot treatment of the haloenoates, haloenones or haloenals with thiols in the presence of organic base leads either to vicinal dithiosubstituted carbonyl-bearing compound or captodative systems with good to excellent yield. The major reaction direction strongly depends on the type of base used. GRAPHICAL ABSTRACT