Dihydro benzene

The syntheses described above in which a benzenoid ortho-dicarbonyl derivative reacts with an amine require two reducing equivalents to proceed smoothly to the isoindole oxidation level. The synthesis described by White and Mann5,68 accommodates this feature by employing a 1,4-dihydro-benzene derivative (Eq. 11). 

Synonyms 1,3-Benzenediol m-Benzenediol Cl 76505 1,3-Dihydroxy-benzene m-Dihydro) benzene m-Dioxybenzene m-Hydroquinone 3-Hydroxycyclohexadien-1-one 3-Hydroxyphenol m-Hydroxyphenol Resorcin Resorcine Classification Aromatic alcohol phenol Empirical CsHsOj Formula C6H,(OH)2... 

A soln. of the startg. m. in anhydrous tetrahydrofuran treated with powdered Na-methoxide, and refluxed 2 hrs. -> N-carbomethoxyazepine. Y 66.9%. - This is the flnal stage of a general multi-step synthesis of IH-azepines from 1,4-dihydro-benzenes. F. e. s. L. A. Paquette et al., J. Org. Chem. 34, 2866 (1969). 

The alfin polymerization yields extremely high-molar mass poly (butadienes) with 65%-75% transAA structures. 1,4-Dihydro benzene or 1,4-dihydro-naphthalene serve as regulators to control the molecular weights. Industrially produced butadiene copolymers contain 5%-15% styrene or 3%-10% isoprene. 

Gillette, J. R., Watland, D. and Kalnitsl, G. (1955) Some properties of the manganese and copper catalyzed oxidation of catechol and some other ortho-dihydro benzene derivatives, Biochim. Biophys. Acta 16 51-57. 

AlClj Alkylation Process. The first step in the AIQ. process is the chlorination of / -paraffins to form primary monochloroparaffin. Then in the second step, the monochloroparaffin is alkylated with benzene in the presence of AIQ. catalyst (75,76). Considerable amounts of indane (2,3-dihydro-lH-indene [496-11-7]) and tetralin (1,2,3,4-tetrahydronaphthalene [119-64-2]) derivatives are formed as by-products because of the dichlorination of paraffins in the first step (77). Only a few industrial plants built during the early 1960s use this technology to produce LAB from linear paraffins. The C q—CC olefins also can be alkylated with benzene using this catalyst system. 

Tetracyanoethylene oxide [3189-43-3] (8), oxiranetetracarbonitnle, is the most notable member of the class of oxacyanocarbons (57). It is made by treating TCNE with hydrogen peroxide in acetonitrile. In reactions unprecedented for olefin oxides, it adds to olefins to form 2,2,5,5-tetracyanotetrahydrofuran [3041-31-4] in the case of ethylene, acetylenes, and aromatic hydrocarbons via cleavage of the ring C—C bond. The benzene adduct (9) is 3t ,7t -dihydro-l,l,3,3-phthalantetracarbonitrile [3041-36-9], C22HgN O. 

The fusion of a benzene ring to pyrazine results in a considerable increase in the resistance to reduction and it is usually difficult to reduce quinoxalines beyond the tetrahydroquinoxa-line state (91). Two possible dihydroquinoxalines, viz. the 1,2- (92) and the 1,4- (93), are known, and 1,4-dihydroquinoxaline appears to be appreciably more stable than 1,4-dihydropyrazine (63JOC2488). Electrochemical reduction appears to follow a course anzdogous to the reduction of pyrazine, giving the 1,4-dihydro derivative which isomerizes to the 1,2- or 3,4-dihydroquinoxaline before subsequent reduction to 1,2,3,4-tetra-hydroquinoxaline (91). Quinoxaline itself is reduced directly to (91) with LiAlH4 and direct synthesis of (91) is also possible. Tetrahydroquinoxalines in which the benzenoid ring is reduced are well known but these are usually prepared from cyclohexane derivatives (Scheme 30). 

Terephthalic acid has been obtained from a great many /)-disubstituted derivatives of benzene or cyclohexane by oxidation with permanganate, chromic acid, or nitric acid. The following routes appear to have preparative value from />-toluic acid, />-methylacetophenone,2 or dihydro-/)-tolualdehyde by oxidation with permanganate from f>-cymene by oxidation with sodium dichromate and sulfuric acid from />-dibromobenzene or from /i-chloro- or -bromobenzoic acid by heating at 250° with potassium and cuprous cyanides and from />-dibromo-benzene, butyllithium, and carbon dioxide. ... 

Lithium metal in ammonia at high concentration (4 M), with an alcoholic proton donor, will reduce the benzene ring of a phenoxide ion. The lithium salt of estrone is reduced under such conditions in 95% yield to a mixture containing 77% of estr-5(10)-ene-3a,17i -diol and 23% of the derived 5(10)-dihydro derivative. 

Arylation of enamines with p-benzoquinones takes a somewhat different course (70). The enamine (16) reacts exothermally with p-benzoquinone in benzene solution to give 2-(dimethylamino)-2,3-dihydro-3,3-dimethyl-5-benzofuranol (92). The reaction of enamines with quinone dibenzenesul-fonimide proceeds similarly (68). The product from the enamine (28) is the tetrahydrocarbazole derivative (93). 

Nuclear magnetic resonance measurements have led to the conclu-sion that 2-pyridones have about 35% of the aromaticity of benzene and that the formally related l,2-dihydro-2-methylenepy-ridine is not aromatic. A substantial contribution by such resonance is indicated by the electronic spectrum of 2-quinolone, which is... 

Finally, there is a series of publications by Prinzbach and co-workers on 4,7-dihydro-l//-l,4,7-triazonine 42b (80CB3127, 80CB3161, 88CB757, 89AG1386). Tliis compound, obtained by a 3valence isomer) is a nonaromatic, nonplanar 127r-electron system, better represented as 42c. 

The cyclization of l-dialkylaminobut-l-en-3-ynes with l-amino-2-mercapto-benzene occurs with the same ease (0°C, EtaO, 20 min), the yieldof2-dialkylamino-4-methyl-5//-1,5-dihydro-1,5-benzothiazepines (107) reaching 87 and 91% (85USSRP1130565 88ZOR88). 

Irradiation of 9-substituted 6-oxo-3,4-dihydro-2//,6//-pyrido[l,2-Z)]-[1,3]thiazine-4-carboxylate 93 in benzene afforded tricyclic derivatives 94, sometimes as a diastereomeric mixture (00JCS(P1)4373). 

Reaction of 2-cyano-3-(4-methoxyphenyl)acroyl chloride and 2-amino-pyridine in boiling benzene in the presence of NEt3 for 5 h gave a 2 1 mixture of 3-cyano-4-(4-methoxyphenyl)-3,4-dihydro-2//-pyrido[l, 2-n]pyr-imidin-2-one and 2- [2-cyano-3-(4-methoxyphenyl)acroyl]amino pyridine (01SUL151). 

It is understandable that dihydro adducts should be formed by polycyclic compounds and not by benzene or pyridine, because the loss of aromatic resonance energy is smaller in the former than in the latter process, (c) When dibenzoyl peroxide is decomposed in very dilute solution (0.01 Af) in benzene, 1,4-dihydro biphenyl is produced as well as biphenyl, consistent with addition of the phenyl... 

Three tautomeric structures (1,2-dihydro 27, 1,4-dihydro 28, and 3,4-dihydro 29) are possible for N-unsubstituted dihydroquinolines, which retain the aromatic benzene ring, and two structures 27 and 28 for N-substituted derivatives. No information on the tautomerism of such dihydroquinolines and stability of the possible tautomers was available when the earlier review (76AHCS1) was published. 

One gram of 6,7-dihydro-5H-dibenz[c,e] azepine hydrochloride was dissolved in water, made alkaline with concentrated ammonia, and the resultant base extracted twice with benzene. The benzene layers were combined, dried with anhydrous potassium carbonate, and mixed with 0.261 g of allyl bromide at 25°-30°C. The reaction solution became turbid within a few minutes and showed a considerable crystalline deposit after standing 3 A days. The mixture was warmed VA hours on the steam bath in a loosely-stoppered flask, then cooled and filtered. The filtrate was washed twice with water and the benzene layer evaporated at diminished pressure. The liquid residue was dissolved in alcohol, shaken with charcoal and filtered. Addition to the filtrate of 0.3 gram of 85% phosphoric acid in alcohol gave a clear solution which, when seeded and rubbed, yielded 6-allyl-6,7-dihydro-5H-dlbenz[c,e] azepine phosphate, MP about 211°-215°C with decomposition. 

To a solution of 10 g of 2-N-methyl-aminoacetamido-3-o-chlorobenzoyl-5-ethylthiophene in 50 ml of pyridine are added 20 ml of benzene and 1.9 g of acetic acid. The resulting mixture is refluxed with stirring for 10 hours in a flask provided with a water-removing adaptor. The reaction mixture is concentrated, and the residue is extracted with chloroform. The chloroform layer is washed with water and then with a sodium hydrogen carbonate solution, then dried over magnesium sulfate. The chloroform is distilled off under reduced pressure, and toluene is added to the residue. Thus is precipitated white crystalline-5-o-chloropheny -7-ethyl-1 -methyi-1,2-dihydro-3H-thieno-[2,3-e] [ 1,4] diazepin-2-one, MP 105°C to 106°C. 

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