2,5-Bis(vinyloxyalkylamino)-1,4-benzoquinones

Russian Journal of Organic Chemistry -     

Cine-substitution in reactions of dichloro-1,4-benzoquinones with pyrrolidine

Products ofcine-substitution are formed in reactions of 2,5- and 2,6-dichloro-1,4-benzoquinones with pyrrolidine. The main reason for amination of chloroquinones by pyrrolidinevia the mechanism ofcine-substitution is the high basicity of this amine. A high degree of localization of the -bond in the molecules of the starting chloroquinones and the strong conjugation of the amino group with the quinone ring in the molecules of the intermediate monoaminoquinones are two other factors that favor an increase in yields of the products ofcine-substitution.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2702–2709, November, 1996.     

Cyclic voltammetry and theoretical calculations of silyl-substituted 1,4-benzoquinones

Cyclic voltammograms of 2,3,5,6-tetrakis(trimethylsilyl)-1,4-benzoquinone (1a), 2,3,5,6-tetrakis(dimethylvinylsilyl)-1,4-benzoquinone (1b), 2,3,5,6-tetrakis(dimethylsilyl)-1,4-benzoquinone (1c), 4,4,6,6,10,10,12,12-octamethyl-4,6,10,12-tetrasilatricyclo[7.3.0.0^3,7]dodeca-1(9),3(7)-diene-2,8-dione (1d), and 5-t-butyl-2-(pentamethyldisilanyl)-1,4-benzoquinone (5h) showed that the first reduction step was reversible and that the second step was irreversible. The first half-wave reduction potentials of 1a, 1b, 1c, and 1d shifted negatively relative to 1,4-benzoquinone by −0.31, −0.24, −0.03, and −0.18 V, respectively. These results demonstrated that the electron-accepting ability of the chair-form quinones 1a and 1b was lower than that of the planar quinones 1c and 1d. The of 5h (−0.93 V vs. Ag/Ag⁺) was quite similar to that of 5-t-butyl-2-trimethylsilyl-1,4-benzoquinone (5a, −0.94 V). A cyclic voltammogram of dimethylsilylene-bridged 1,4-benzoquinone dimer 7 showed two kinds of (−0.76 and −0.94 V). The electrochemical behavior of 7 would be interpreted in terms of near-neighbor interactions between reduced and non-reduced quinone units. Theoretical calculations of the silyl-1,4-benzoquinones reproduced well the solid state structures of the compounds. Also, the computed vibrational frequencies of the silyl-1,4-benzoquinones were in good agreement with the IR absorption frequencies of the CO units in the compounds. The LUMO energy levels of the silyl-1,4-benzoquinones were quantitatively proportional to the .     

1,3-Dipolar cycloaddition reactions of 1,4-benzoquinones with nitrilimines

The cycloaddition reactions of some aryl conjugated p-benzoquinones with nitrilimines were studied. Depending upon the reaction conditions mono- and/or bis- adducts were isolated only from carbon-carbon double bond. The structure determination was unequivocally established by an X-ray analysis carried out on a bis-adduct. The observed regio-, as well as site-selectivity, was qualitatively correlated with frontier molecular orbitals of the reacting species.     

Isomerization of Diels-Alder Adducts of Benzoyl-1,4-benzoquinones: A Route to the Anthracyclinone Ring system

Base-induced [1,5laroyl migration in the Diels-Alder adduct of [2-(1,3-dioxolan-2-yl)benzoyl]-1, 4-benzoquinone and trans-penta-1, 3-diene followed by acid-mediated cyclisation affords the corresponding hydroxynaphthacenequinone.     

Radical addition of methyldichlorosilane to ketones

Radiation-induced reaction of methyldichlorosilane with ketones is shown to form products of radical addition to the carbonylic group. Competition kinetics method was used to determine relative rate constants of methyldichlorosilyl radical addition to some ketones.

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Oxidation of 4-methoxyanilines to 1,4-benzoquinones using ceric ammonium nitrate (CAN)

Treatment of substituted 4-methoxyanilines with ceric ammonium nitrate in a 1:1 mixture of water and acetonitrile resulted in the formation of 1,4-benzoquinones in acceptable yields.     

Synthesis of amino-1,4-benzoquinones and their use in Diels-Alder approaches to the aminonaphthoquinone antibiotics

A new protocol for the synthesis of protected amino-1,4-benzoquinones by oxidation of the corresponding 2,5-dimethoxyaniline derivatives using PhI(OAc)(2) or PhI(OCOCF(3))(2) in water containing 2.5% methanol is reported. The process represents an improvement over previously reported methods, both in terms of yield and number of steps, and in the range of nitrogen protecting groups that it tolerates. A number of novel aminobenzoquinones were prepared and subsequently used as dienophiles in Diels-Alder reactions to form building blocks for the synthesis of the aminonaphthoquinone antibiotics such as salinisporamycin.     

Radical addition of methyldichlorosilane to vinyl acetate

The GC-MS method was used to identify the addition products of methyldichlorosilane to vinyl acetate. Radiation-induced addition of methyldichlorosilane to vinyl acetate produces 2-methyldichlorosilylethyl ethyl ether. The reaction follows a radical-chain mechanism. The ratio of the rate constants of methyldichlorosilyl radical addition to C=C and C=O to vinyl acetate amounts to 0.4±0.1 (303 K).

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- . , - 2- . , C=C C=O 0,4±0,1.

     

Nucleophilic addition of acetophenone to 1,4-diethynylbenzene

Russian Journal of Organic Chemistry -     

Radical addition to 2-isopropenyl-5-butoxyoxazole

The preparation and the spectroscopic analysis of a dimeric adduct ( V ) obtained from 2-isopropenyl-5-butoxyoxazole ( III ) and α,α-azobis-isobutyronitrile (AIBN) ( IV ) are reported. It is noteworthy that ( III ) inhibits completely the homopolymerization of styrene. This is in strong opposition to the facile homopolymerization and copolymerization of 2-isopropenyl-4,5-dimethyloxazole with styrene. The smooth formation of ( V ) is also in sharp contrast to the lack of reactivity of ( III ) towards cationic initiators.     

Oxidative free radical reactions between 2-amino-1,4-benzoquinones and carbonyl compounds

The manganese(III) initiated oxidative free radical reactions of 2-amino-1,4-benzoquinone are described. The free radical reaction of 5,6-dimethyl-2-methylamino-1,4-benzoquinone (1) provides a novel method for the synthesis of indole-4,7-dione and indole-2,4,7-trione. High chemoselectivity was observed in different solvents. The regioselectivity of this reaction was also studied with 5-methyl-2-methylamino-1,4-benzoquinone (19). In most cases, indole-4,7-diones 20 and 21 were produced in high regioselectivity.