Yu. S. Shabarov

Mercuration of some styrenes and phenylcyclopropanes. The effect of the aromatic nitro group on reductive demercuration with sodium borohydride

Abstract Mercuric acetate reacts with o - and p -nitrostyrenes and with nitrophenylcyclopropanes in methanol or glacial acetic acid to give β- and γ-mercurated nitroderivatives, respectively. In contrast to the nitrostyrenes, mercuration of the corresponding nitrophenylcyclopropanes only occurs in the presence of perchloric acid as catalyst. 2,4-Dinitrophenylcyclopropane does not react with mercuric acetate even under the catalysis conditions. Aromatic nitro groups decelerate reductive demercuration of γ-mercurated alcohols and their derivatives with sodium borohydride to the extent that other fragments of the molecule may undergo reduction while the HgX function remains intact. This result may be explained by intermolecular coordination of the nitro group to the mercury atom, which reduces effective positive charge on the metal and hinders the attack by the reducing reagent.

Mercuration of phenyl cyclopropanes: spatial factors

Mercuration of trans-1-phenyl-2-cyclohexylcyclopropane and stereoisomeric 1,2-di- and 1,2,3-triphenylcyclopropanes has been studied. An increase in the number of substituents in the cyclopropane ring leads to an increase in the stability of the ring towards mercury acetate, and substitution in the aromatic ring is the main process with 1,2,3-triphenylcyclopropane.

Synthesis of 1,3-dihydro-5(r)-7,8-ethylenedioxy-2h-1,4-benzo-diazepin-2-ones

Abstract1,4-Diazepin-2-ones have been prepared from 1,4-benzodioxine for the first time.

New Pathway to the Synthesis of Substituted 4H-3,1-Benzoxazines

The intramolecular rearrangement of N-acyl-2-cyclopropylanilines by the action of protic acids gives substituted 4H-3,1-benzoxazines. The reaction proceeds in high yield through the formation of benzoxazine precursors, namely, the corresponding 3,1-benzoxazinium ions, which are stable in acid solution. N-Acylamino-2-alkenylbenzenes, in which the double bond of the alkyl chain is conjugated with the benzene ring, are capable of undergoing a similar rearrangement.

Synthesis of isoxazolines from arylcyclopropanes under nitrosation conditions

It is shown that the corresponding isoxazolines are formed in high yields when aryl-, diaryl-, and alkylarylcyclopropanes are treated with sodium nitrite in trifluoroacetic or trichloroacetic acid at 0 °C. The reaction does not take place in acetic or chloroacetic acid. A possible mechanism for the formation of the isoxazolines is proposed. The latter were subjected to a mass-spectrometric study.

Nitration of 5-formyl-substituted 2-cyclopropylfurans and 2-methylfurans and the corresponding thiophenes

In the nitration of 5-formyl-substituted 2-cyclopropylfurans and the corresponding thiophenes, in addition to the formation of the corresponding 3-nitro derivative the replacement of the formyl group by a nitro group takes place. For a thiophene derivative the latter direction of the reaction is observed to a substantially smaller degree. Under nitration conditions, 5-formylsylvane is converted only into 5-nitrosylvane, while the corresponding formylmethylthiophene is nitrated exclusively in position 3. The difference observed in the behavior on nitration of the furans and thiophenes studied is explained by the different degrees of participation of the heteroatom in the delocalization of the charges in the heterocyclic ipso-ions formed as intermediates.

Ipso attack in the nitration of 5-bromo- and 5-methyl-2-cyclopropylthiophenes

It was established that 5-bromo-2-cyclopropylthiophene and 5-methyl-2-cyclo-propylthiophene undergo transformations during nitration with nitric acid in acetic anhydride that are a consequence of ipso attack of the nitryl cation in the 2 or 5 positions of the thiophene rings of the starting compounds.

Heterocyclic Ions From N-Oxides of N-(4-Nitrobenzylidene)-2-cyclopropylaniline and N-(4-Nitrobenzylidene)-2-cyclopropylmethylniline: Formation, Isomerization, and Conversions

The N-oxide of N-(4-nitrobenzylidene)-2-cyclopropylaniline is converted by the action of strong acids into the corresponding 2,1-benzoxazinium derivative. Under identical conditions the N-oxide of N-(4-nitrobenzylidene)-2-cyclopropylmethylaniline forms the corresponding 2,1-benzoxazinium and 2,1-benzoxazepinium salts in a ratio of 1 : 2. The 2,1-benzoxazepinium ions are thermodynamically less stable and are isomerized with time into 2,1-benzoxazinium ions. Treatment of 2,1-benzoxazinium salts with hydrobromic acid solution and subsequent neutralization leads to o-(2-hydroxyalkyl)anilines and p-nitrobenzaldehyde. The effect of the nature of the ortho substituent on the direction of the conversions of the corresponding arylcyclopropanes is discussed.

2-Cyclopropylbenzoic acids in the synthesis of phthalides and 3,4-dihydroisocoumarins

Abstract2-Cyclopropylbenzoic acids, under the action of strong protic acids (FSO3H, H2SO4), are converted to 3-ethylphthalidium ions. In solutions in these inorganic acids, the 3-ethylphthalidium ions are isomerized to 3-methyl-3,4-dihydroisocoumarinium ions. As a result, a thermodynamic equilibrium is established, with the concentrations of both types of cyclic ions depending on the nature of the substituent in the aromatic part of the substrate. Neutralization of the original solutions of 3-ethylphthalidium ions or a mixture of these with 3-methyl-3,4-dihydroisocoumarinium ions, gave either 3-ethylphthalides or their mixtures with 3-methyl-3,4-dihydroisocoumarins. The neutral 3-ethylphthalides and 3-methyl-3,4-dihydroisocoumarins, when subjected to the action of inorganic acids, are also isomerized to form in each case a mixture of ions with concentrations matching the concentrations of ions formed from the corresponding 2-cyclopropylbenzoic acids.

Synthesis and biological activities of substituted 2- and 3-chloropropylthiophenes

Beginning in 1970 we have systematically studied the potential reactivities and biological properties of several thiophene derivatives. In these studies special attention was paid to development of synthetic methods for various functionally substituted cyclopropylthiophenes. It was proposed that the strength of the electronic bonds in the triangular ring would confer special biological properties on its derivatives. Particular attention was paid to obtaining cyclopropylthiophenes substituted with electron-accepting groups in the heterocyclic ring, which according to the literature [2] increases the antibacterial activity of several medicinal compounds in comparison with unsubstituted analogs or analogs substituted with electron-donating groups.