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.     

Reactions of N-substituted 2,6(3,5)-dialkyl-1,4-benzoquinone imines with arenesulfinic acids

The regioselectivity in the reactions of N-arylsulfonyl-2,6-dialkyl-1,4-benzoquinone imines with arenesulfinic acids (1,6-, 6,1-, or 6,3-addition) is determined by steric factor, while in the reactions of N-aroyl-1,4-benzoquinone imines electronic effect of substituents in the quinoid ring is crucial. The reactions of N-arylsulfonyl-3,5-dimethyl-1,4-benzoquinone imines with arenesulfinic acids follow mainly the 1,4-addition pattern. N-(N-Arylsulfonylbenzimidoyl)-1,4-benzoquinone imines are capable of reacting in a way similar to both N-arylsulfonyl and N-aroyl derivatives.     

Reaction of some <Emphasis Type="Italic">N</Emphasis>-substituted 1,4-benzoquinone imines with sodium azide

The reactions of N-(arenesulfinyl)-1,4-benzoquinone imines with sodium azide afforded the corresponding N-(arylsulfanyl)-2-azido-1,4-benzoquinone imines via 1,4-addition of azide ion and subsequent intramolecular oxidation–reduction.     

Reaction of <Emphasis Type="Italic">N</Emphasis>-sulfonyl-1,4-benzoquinone imines with sodium azide

Depending on the conditions and the order of addition of the reactants, reactions of N-sulfonyl-1,4-benzoquinone imines with sodium azide afforded N-(3-azido-4-hydroxyphenyl)alkane(arene)sulfonamides, N-(3-azido-4-oxocyclohexa-2,5-dienylidene)alkane(arene)sulfonamides, and N-(3,5-diazido-4-hydroxyphenyl)-alkanesulfonamides. Quantum chemical calculations showed that the reactions begin with addition of azide ion to the quinone imine.     

Reaction of N-phenyl(benzylidene,phenoxy)acetyl-1,4-benzoquinone imines with sodium azide

N-Phenyl(benzylidene, phenoxy)acetyl-1,4-benzoquinone imines reacted with sodium azide to give the corresponding 1,4-addition products, N-(4-hydroxyphenyl) carboxamides. Quantum chemical calculations showed that the initial step in the examined reaction is addition of azide ion to neutral quinone imine molecule.     

Activated sterically strained C=N bond in <Emphasis Type="Italic">N</Emphasis>-substituted <Emphasis Type="Italic">p</Emphasis>-quinone mono- and diimines: XV. Synthesis,structure, and reactions with alcohols of <Emphasis Type="Italic">N</Emphasis>-carbamoyl-1,4-benzoquinone imines

The reaction of 4-aminophenols with N-nitrourea or with sodium cyanate in acetic acid gave the corresponding 4-ureidophenols which were oxidized to N-carbamoyl-1,4-benzoquinone imines, substituted N-(4-oxocyclohexa-2,5-dien-1-ylidene)ureas. N-(2,6-Dimethyl-4-oxocyclohexa-2,5-dien-1-ylidene)urea possessing activated sterically strained C=N bond reacted with alcohols to afford N-(1-alkoxy-2,6-dimethyl-4-oxocyclohexa-2,5-dienyl)ureas.     

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.     

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).     

Reactivity of N-arylsulfonyl-1,4-benzoquinone imines. Reaction with hydrazoic acid

N-Arylsulfonyl-2-halo-1,4-benzoquinone imines react with hydrazoic acid in boiling acetic acid via two pathways: the 1,4-addition and nucleophilic replacement of the halogen atom by an azido group, followed by the 1,4-addition of HN₃. In the reaction of N-arylsulfonyl-2,6-dihalo-1,4-benzoquinone imines with hydrazoic acid, both halogen atoms are replaced by azido groups, while N-p-tolylsulfonyl-2-methyl-1,4-benzoquinone imine takes up HN₃ molecule according to the 1,4-addition pattern.     

Reaction of <Emphasis Type="Italic">N</Emphasis>-arenesulfonyl-1,4-benzoquinone imines with acetylacetone

N-Arenesulfonyl-1,4-benzoquinone imines reacted with acetylacetone to afford different products, depending on the isolation procedure. Crystallization from polar protic solvents gave N-[4-hydroxy- 3-(2-hydroxy-4-oxopent-2-en-3-yl)phenyl]arenesulfonamides and 6-(2-oxopropyl)-4-(arenesulfonamido)phenyl acetates, whereas N-(3-acetyl-2,6-dimethyl-1-benzofuran-5-yl)arenesulfonamides were isolated by crystallization from nonpolar aprotic solvents.     

Reaction of <Emphasis Type="Italic">N</Emphasis>-chloro-1,4-benzoquinone imines with thiols

N-Chloro-1,4-benzoquinone imines reacted with arenethiols to give different products, depending on the conditions and initial quinone imine structure. N-(Arylsulfanyl)-1,4-benzoquinone imines were obtained as a result of nucleophilic substitution of the chlorine atom, and 1,4-benzoquinone imines containing an aryl-sulfanyl substituent in the quinoid ring were formed according to the radical mechanism. The reactions of N-chloro-1,4-benzoquinone imines with heterocyclic thiols afforded only the corresponding chlorine substitution products.     

Comparison of preparation methods of N-arylsulfinyl-1,4-benzoquinone monoimines

Advantages and shortcomings were discussed of three procedures for preparation N-arylsulfinyl-1,4-benzoquinone imines: the reaction of arenesulfenyl chlorides with 1,4-benzoquinone oximes, the oxidation of N-arylthio-1,4-benzoquinone imines, and the reaction of arylsulfinyl chlorides with p-aminophenols followed by oxidation. A series of new N-arylsulfinyl-1,4-benzoquinone imines was obtained.     

Reaction of <Emphasis Type="Italic">N</Emphasis>-alkyl(aryl)aminocarbonyl-1,4-benzoquinone monoimines with alcohols

Reactions of N-alkyl(aryl)aminocarbonyl-3,5-dimethyl-1,4-benzoquinone monoimines with alcohols led to the formation of products of 1,2-addition, quinolide compounds. They are the final products in reactions with alkyl derivatives, but in event of aryl derivatives they underwent cyclization with the subsequent elimination of the alcohol molecule to provide 4,7a-dimethyl-1-aryl-7,7a-dihydro-1H-benzimidazole-2,6-diones.     

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 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.     

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.     

Reaction of N-arylcarbamoyl-1,4-benzoquinone imines with sodium arenesulfinates

N-Arylcarbamoyl-1,4-benzoquinone imines possessing at least one free ortho position with respect to the carbonyl carbon atom in the quinoid ring react with sodium arenesulfinates according to the nucleophilic 1,4-addition pattern with complete regioselectivity. If both ortho positions are occupied, the reaction gives a mixture of products where the major ones are 1,6- and 6,1-adducts formed according to the radical ion mechanism.     

An efficient chemoenzymatic approach to enantiomerically pure 4-[2-(difluoromethoxy)phenyl] substituted 1,4-dihydropyridine-3,5-dicarboxylates

An efficient chemoenzymatic synthesis of (−)-3-methyl 5-(2-propoxyethyl) (4R)-4-[2-(difluoromethoxy)phenyl]-2,6-dimethyl-1,4-dihydro-3,5-pyridinedicarboxylate has been achieved. The key step is a highly stereoselective Candida rugosa lipase (CRL)-mediated asymmetrisation of the prochiral bis[(isobutyryloxy)methyl]-4-[2-(difluoromethoxy)phenyl]-1,4-dihydro-2,6-dimethyl-3,5-pyridinedicarboxylate.     

Reaction of N-substituted 2,5-dialkyl-1,4-benzoquinone imines with arenesulfinic acids

Reactions of N-aroyl-, N-arylsulfonyl-, and N-(N-arylsulfonylbenzimidoyl)-2,5-dialkyl-1,4-benzoquinone imines with sodium arenesulfinates in acetic acid gave the corresponding 1,4-, 6,1-, and 1,6-addition products. Variation of the size and donor power of substituents in positions 2 and 5 of the quinoid ring almost does not affect the ratio of the addition products, which is determined mainly by the nature of substituent on the nitrogen atom.     

Chlorination of N-acyl Derivatives of p-Aminophenols (Naphthols) and p-Phenylenediamines

The chlorination of N-acyl derivatives of p-aminophenols can provide either N-acyl-2,3,6-trichloro-4-aminophenols or N-acyl-2,3,5,6-tetrachloro-1,4-benzoquinone imines depending on solvent nature, process temperature, and molar ratio initial compound-chlorine. The chlorination of N-acyl-4-amino-1-naphthols affords only N-acyl-2,3-dichloro-1,4-naphthoquinone imines. N,N'-Diacyl-1,4-phenylenediamines give rise on chlorination to a mixture of 2,5-dichloro-, 2,6-dichloro-, and 2,3-dichloro-N,N'-diacyl-1,4-phenylenediamines.