A. N. Fedotov

Synthesis of o-nitrosoacylbenzenes from o-nitrobenzyl alcohols and their derivatives

Nitration of substituted benzyl alcohols, as well as ethers and esters derived therefrom, with nitric acid in acetic anhydride was studied. The corresponding o-nitrobenzyl alcohols and their derivatives formed as the primary products are capable of being converted into o-nitrosoacylbenzenes by the action of acids.

1,1-Dihalo-2-benzycyclopropanes in reaction with nitrous acid

Interaction of 1,1-dichoro and 1,1-dibromo-2-benzylcyclopropanes with nitrous acid generated in situ was studied. It was shown that both nitration of the aromatic ring and heterocyclization of 1,1-dihalo-2-benzylcyclopropanes take place. Heterocyclization is initiated by opening of the cyclopropane ring in the reaction with nitrosyl cation. The nature of halogen atom in the cyclopropane ring affects the regioselectivity of the reactions.

N-acylaminophenylcyclopropanes in reaction with nitrous acid generated in situ

The reaction of N-acylaminophenylcyclopropanes with HNO2 proceeds regioselectively with introduction of an N = O fragment into the three-membered ring and formation of the corresponding Δ2-isoxazolines. For ortho-substituted N-acylaminophenylcyclopropanes side processes were observed, caused by the intramolecular participation of the N-acyl group in conversions of the carbenium ions formed on opening the cyclopropane ring under the action of the nitrosating reagent, and by direct insertion of the modified ortho substituent into the three-membered ring.

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.

Direct synthesis of ethers from aldehydes and ketones. One-pot reductive etherification of benzaldehydes, alkyl aryl ketones, and benzophenones

Benzyl alcohols formed by the reduction of benzaldehydes, alkyl aryl ketones, and benzophenones with sodium tetrahydridoborate in alcohols undergo in situ etherification with the solvent in the presence of a catalytic amount of HCl. Thus the process may be regarded as one-pot transformation of carbonyl compounds into the corresponding benzyl ethers. The yields of ethers depend on the substituent nature in the aromatic fragment of the initial carbonyl compound and on the alcohol used as reduction medium.

Hydrochloric acid as an efficient catalyst for intermolecular condensation of alcohols. A simple and highly efficient synthesis of unsymmetrical ethers from benzylic alcohols and alkanols

Benzylic alcohols and diarylmethanols with electron-donating substituents in the aromatic ring reacted with aliphatic alcohols in the presence of a catalytic amount of HCl to give the corresponding alkyl arylmethyl ethers. The reactivity of diarylmethanols in the intermolecular dehydration depended on the nature of substituents in the aromatic rings and structure of aliphatic alcohol.

Benzyl-4,5-dihydroisoxazoles from benzylcyclo-propanes: regioselective insertion of an n=o fragment into the three-membered carbocycle of benzylcyclopropanes by the action of nitrous acid

The action of equimolar amounts of nitrous acid formed in situ on benzylcyclopropanes with electron-donor and electron-withdrawing substituents in the aromatic part of the substrate lead, at certain temperatures, exclusively to the insertion of an N=O fragment into the three-membered carbocycle with subsequent formation of a heterocyclic isoxazoline (4,5-dihydroisoxazole) system.

Heterocyclization of trans-1,2,3-triphenyl-cyclopropane using nitrous acid

It is known that phenyland 1,2-diphenylcyclopropanes react readily with an equivalent of nitrous acid to form 5-phenyland 3,5-diphenyl-4,5-dihydroisoxazoles. The geometry of the benzene rings in the 1,2-diphenylcyclopropanes has virtually no effect on the yield of the corresponding heterocycles [1, 2]. Since not only monoand disubstituted isoxazolines and isoxazoles but also triarylisoxazolines (and isoxazoles) are of interest for practical use [3], but synthetic methods of the latter are quite limited, we have tried to find out whether 1,2,3-triphenylcyclopropanes are converted to products of N=O fragment insertion into the three-carbon ring by the action of nitrous acid using the conditions reported in [1, 2]. It was shown that treatment of trans-1,2,3-triphenylcyclopropane (1) with an equivalent amount of sodium nitrite in trifluoroacetic acid gave only trans-3,4,5-triphenyl-4,5-dihydroisoxazole (2). This result shows that triphenylcyclopropanes can be used successfully in the synthesis of the corresponding isoxazolines.

Reaction of substituted 7-cyclopropyl-1,4-benzodioxanes with dinitrogen tetraoxide

The reaction of 6-bromo-7-cyclopropyl-1,4-benzodioxane with N2O4 in methylene chloride does not affect the cyclopropane ring and forms the nitrodebrominated product (ipso-substitution). The same reaction of 6-nitro- and 5,6-dinitro-7-cyclopropyl-1,4-benzodioxanes produces only the products with an modified threemembered ring. The difference in the reaction paths of the studied cyclopropylbenzodioxanes with N2O4 is explained by the different ratio of substrate to one-electron oxidant, the nitrosyl cation.

o-Acylbenzonitriles: Synthesis and Heterocyclization under Acid Hydrolysis of the Cyano Group

Abstract2-Cyanobenzophenones were synthesized by reaction of 2-bromobenzophenones with copper(I) cyanide in DMF, and their transformations involving acid hydrolysis of the cyano group were studied. Reactions of o-benzoylbenzonitriles with trifluoroacetic acid in the presence or in the absence of sulfuric acid afforded 3-hydroxyphthalimidines in high yields. Under analogous conditions, benzonitriles having no acyl group in the ortho position were converted to the corresponding benzamides. 2-Cyanobenzophenones reacted with sulfuric acid in the absence of trifluoroacetic acid to give only substituted anthraquinones.