Halogenation of N-substituted p-quinone monoimines and p-quinone monooxime esters: X. Halogenation of N-aroyl-2,5(2,3)-dialkyl-1,4-benzoquinone monoimines and their reduction products

Introduction of a strong electron-withdrawing substituent to the nitrogen atom of 2,5(2,3)-dialkyl-1,4-benzoquinone imines makes their halogenation products, the corresponding cyclohexene derivatives, very unstable and favors halogenation of methyl groups in the quinoid ring. Bromination of 4-amino-N-aroyl-2,5-dialkyl-6-bromophenols gave 2,5-dialkyl-6-benzoyloxy-3,5-dibromocyclohex-2-ene-1,4-diones.     

Halogenation of N-substituted p-quinone monoimines and p-quinone monooxime esrers: XI. Synthesis and halogenation of 4-[aryl(alkyl)aminocarbonyl-oxyimino]cyclohexa-2,5-dien-1-ones

4-[Aryl(alkyl)aminocarbonyloxyimino]cyclohexa-2,5-dien-1-ones were synthesized by treatment of various substituted p-quinone monooximes with aryl isocyanates. The selectivity in the halogenation of the obtained p-quinone monooxime esters depended on the substrate structure and was either completely (syn addition) or partly regioselective (syn or anti addition). In all cases, the effect of steric factor was crucial, and the reaction was accompanied by halogenation of the aryl fragment.     

Halogenation of N-substituted p-quinone imines and p-quinone oxime esters: IV. Chlorination and bromination of N-arylsulfonyl-2(3)-methyl(2-chloro)-1,4-benzoquinone monoimines

The addition of halogens to N-arylsulfonyl-1,4-benzoquinone imines, which exist in a solution as Z and E isomers, is controlled by the steric factor. Z-E Isomerization strongly affects the stability of cyclohexene structures formed by halogenation of 1,4-benzoquinone imines. The halogenation of N-arylsulfonyl-1,4-benzoquinone imines was found to be accompanied by prototropic rearrangement.     

Thiocyanation of N-aryl,N-acetyl,and N-[arylsulfonylimino(methyl)methyl] derivatives of 1,4-benzoquinone monoimine

N-[arylsulfonylimino(methyl)methyl] derivatives of 1,4-benzoquinone monoimine with alkyl substituents in the quinoid ring have been synthesized and their spectral characteristics were determined. The thiocyanation of N-aryl, N-acetyl, and N-[arylsulfonylimino(methyl)methyl] derivatives of 1,4-benzoquinone monoimine depending on the LUMO energy of the initial quinone monoamine affords derivatives of benzo[d][1,3]oxathiol-2-ones and benzo[d]oxazole-2(3H)-thiones.     

Halogenation of N-substituted para-quinone monoimines and para-quinone monoximes ethers: IX. Halogenation of N-aroyl-2,6(3,5)-dimethyl-1,4-benzoquinone monoimines and their reduced forms

At the halogenation of N-aroyl-2,6(3,5)-dimethyl-1,4-benzoquinone imines we found the halogenation of methyl groups to occur. The bromination of N-aroyl-2,6-dimethyl-1,4-benzoquinone imines yielded 3,6-dibromo-2,6-dimethyl-5-aroyloxycyclohex-2-ene-1,4-diones due to the strong acceptor property of the ArCO group and high redox potentials of N-aroyl derivatives. In the chlorination of N-aroyl-3,5-dimethyl-1,4-benzoquinone imines the chlorine addition to the C=C bond of the quinoid ring proceeded both by the trans- and syn-scheme.     

Halogenation of N-substituted p-quinone monoimines and p-quinone monooxime ethers: XIII. Specificity of bromination of N-Acetyl(aroyl)-1,4-benzoquinone monoimines

6-Hydroxy-2-methyl(aryl)-1,3-benzoxazoles were synthesized by bromination of N-acetyl(aroyl)-1,4-benzoquinone monoimines.     

Reaction of N-acyl-and N-[N-arylsulfonylbenz(acet)imidoyl]-1,4-benzoquinone monoimines with hydrazoic acid

N-Aroyl-3,5-dimethyl-and N-[N-arylsulfonylbenz(acet)imidoyl]-3,5-dimethyl-1,4-benzoquinone monoimines react with hydrazoic acid according to the 1,4-addition pattern. N-Acyl-2,3,5,6-tetrachloro-1,4-benzoquinone monoimines take up hydrazoic acid at the double C=N bond (1,2-addition).     

Reaction of N-acetyl- and N-[1-(arylsulfonylimino)ethyl]-1,4-benzoquinone imines with sodium arenesulfinates

N-Acetyl- and N-[1-(arylsulfonylimino)ethyl]-1,4-benzoquinone imines having no substituent in the 2- and/or 6-position of the quinoid ring react with sodium arenesulfinates preferentially according to the 1,4-addition pattern. The presence of an ArSO₂N group favors radical ion reaction with formation of 1,6-addition products.     

Halogenation of N-substituted para-quinone monoimine and para-quinone monooxime esters: V. Chlorination and bromination of N-arylsulfonyl-1,4-benzoquinone monoimines dialkyl-substituted in the quinoid ring

The direction of halogen addition to N-arylsulfonyl-1,4-benzoquinone monoimines dialkyl-substituted in the quinoid ring is governed by the steric factors: the size and position of the substituent, the halogen volume, and the position of the substituent at the nitrogen. The first stage of halogenation of N-arylsulfonyl-4-aminophenols with two alkyl substituents in the phenylsulfonyl ring largely occurs as electrophilic substitution.     

Hydrohalogenation of <Emphasis Type="Italic">N</Emphasis>-[arylsulfonylimino(phenyl)methyl]-1,4-benzoquinone monoimines having alkyl substituents in the quinoid ring

Hydrohalogenation of N-[arylsulfonylimino(phenyl)methyl]-2,5(3,5)-dimethyl-1,4-benzoquinone monoimines follows exclusively the 1,4-addition pattern, whereas N-[arylsulfonylimino(phenyl)methyl]-2,6-dimethyl-1,4-benzoquinone monoimines take up hydrogen halides according to the 6,3-addition scheme.     

Halogenation of n-substituted p -quinone monoimines and p -quinone monooxime esters: VIII. Halogenation of N -aroyl(arylsulfonyl)-2,6-di- tert -butyl-1,4-benzoquinone monoimines and their reduced forms

Chlorination of N-aroyl(arylsulfonyl)-2,6-di-tert-butyl-1,4-benzoquinone imines gave Z and E isomers of 4-arylsulfonylimino-2,6-di-tert-butyl-5,6-dichlorocyclohex-2-en-1-ones and Z isomers of 4-aroyl-(arylsulfonyl)imino-2,6-di-tert-butyl-5,5,6-trichlorocyclohex-2-en-1-ones, in which the tert-butyl group on the sp ³-hybridized carbon atom occupies exclusively the axial position. The formation of Z/E-isomeric structures is related to configurational stability of the chlorination products. The chlorination of 4-aroylamino-2,6-di-tertbutylphenols was found to be accompanied by replacement of one tert-butyl group by chlorine atom with formation of 4-aroylimino-6-tert-butyl-2,3,5,6-tetrachlorocyclohex-2-en-1-ones. Original Russian Text ? A.P. Avdeenko, V.V. Pirozhenko, O.V. Shishkin, G.V. Palamarchuk, R.I. Zubatyuk, S.A. Konovalova, O.N. Ludchenko, 2008, published in Zhurnal Organicheskoi Khimii, 2008, Vol. 44, No. 6, pp. 818–824. For communication VII, see [1].     

Halogenation of N-substituted para-quinone monoimine and para-quinone monooxime esters: VI. Regular trends in chlorination and bromination of N-arylsulfonyl-1,4-benzoquinone monoimines alkyl-substituted in the quinoid ring

Reactions of halogens with N-arylsulfonyl-1,4-benzoquinone monoimines occur with the formation of a halogenonium ion that either transforms into a carbocation where the first halogen atom adds to the carbon in the ortho-position relative to the carbonyl carbon, or the halogenonium ion adds directly the second halogen atom.     

Activated sterically strained C=N bond in N-substituted p-quinone mono- and diimines: XIV. Reaction of some 3,5-dimethyl-1,4-benzoquinone monoimines with alcohols

Steric strain in the C=N-C fragment in 3,5-disubstituted N-acyl-1,4-benzoquinone monoimines, unlike their N-arylsulfonyl analogs, leads to increase of the C=N-C angle above 130° or twisting of the double C=N bond and loss of planarity of the quinoid ring. This structural transformation enhances the reactivity of the C=N bond so that 1,2-addition of alcohols becomes possible with formation of sterically unstrained cyclohexadienone structure with sp ³-hybridized C⁴ carbon atom.     

Hydrohalogenation of N-acetyl(aroyl)-1,4-benzoquinone monoimines

New N-acetyl-1,4-benzoquinone monoimines alkyl-substituted in the quinoid ring were synthesized. The hydrohalogenation of N-acetyl(aroyl)-1,4-benzoquinone monoimines proceeds exclusively in keeping with the 1,4-addition. The hydrochlorination occurs along the ionic mechanism, in the hydrobromination grows the role of the radical mechanism.     

Halogenation of N-substituted p-quinone imines and p-quinone oxime esters: III. Regioselectivity in the halogenation of N-aroyl(arylsulfonyl)oxyimino-2,5-cyclohexadienones

Halogenation of 4-aroyl(arylsulfonyl)oxyimino-2,5-cyclohexadienones is not accompanied by change of the configuration at the nitrogen atom. p-Benzoquinone oxime ethers and esters take up halogens in a regioselective fashion at the syn-C-C bond of the quinoid ring. The main factor responsible for regioselective addition of halogens is configuration at the nitrogen atom, which determines the stability of intermediate halogenonium ion.     

Activated sterically strained C=N bond in N-substituted p-quinone mono- and diimines: XIII. Reactions of N-alkyl(aryl, trifluoromethyl)sulfonyl-, N-arylsulfinyl- and N-arylsulfanyl-1,4-benzoquinone monoimines with alcohols

Steric strains arising between the substituent atoms at nitrogen (S, SO, or SO₂) and the methyl group located in positions 3 or 5 of the quinoid ring of 3,5-dimethyl-substituted quinone monoimines lead to the increased angle C=N-S. As a result in these quinone monoimines the reactions of 1,2-addition become thermodynamically possible since the formation of quinolide structures with the sp³-hybridized carbon atom removes the steric strain.     

Reaction of N-[aryl(benzylidene,phenoxy)acetyl]-1,4-benzoquinone imines with sodium 4-methylbenzenesulfinate

The reaction of N-[aryl(phenoxy, benzylidene)acetyl]-1,4-benzoquinone imines with sodium 4-methylbenzenesulfinates takes different addition patterns, depending on the LUMO energy and charge distribution over the quinoid ring of the initial quinone imine.