Benzene 1,2,4,5-tetramethoxy

EtOH), is insoluble in benzene or ether, and sparingly in chloroform, but dissolves readily in alkali, the solution darkening in air. The salts are crystalline but unstable. The base forms a crystalline metbiodide and contains two methoxyl and two phenolic hydroxyl groups. On methyla-tion it yields a mixture of corydine and fsocorydine. On exhaustive methylation corytuberine yields eventually trimethylamine and 3 4 5 6-tetramethoxy-8-vinylphenanthrene, m.p. 69°. 

A mixture of 38.6 g (0.1 mol) of 3,4,3, 4 -tetramethoxy-6-(a-acetopropyl)-benzophenone, 5.5 g (0.11 mol) of 100% hydrazine hydrate or 3.52 g (0.11 mol) of hydrazine, and 500 ml of absolute ethanol is boiled for 5 hours. After adding 100 ml of benzene, 400 ml of solvent mixture Is distilled off from the reaction mixture by slow boiling for 3 hours. After cooling for 8 hours, 19 g of 5H-2,3-benzodiazepine derivative are separated from the residue as small, white crystals. The melting point is 133°C to 1 36°C (after recrystallizing from absolute ethanol, 136°C). 

Also as noted above any substituents present have little effect upon such oxidations. In 2,2 -methylenedifuran (118) the rings are attacked simultaneously giving a tetramethoxy derivative.297 Even the bulk of the fert-butyl group has little effect.298 The only marked substituent effect is that exerted by an aromatic (benzene, thiophene, furan) residue which, if directly attached at the 2-position, promotes elimination instead of the addition of another methoxy group. The net process then becomes one of arylation, as when 2-(2-thienyl)furan (119) is oxidized to 120.298 There are reports that acetyl and carboxy groups can be ejected during oxidation, but that ester groups are usually retained.287... 

The term Molecular Clip has been coined for molecules of type 2. That these molecules do indeed possess the geometric features of a clip is apparent from the X-ray structure of the tetramethoxy derivative 3a (Fig. 2) [lla,b]. The o-xylylene moieties of this molecule define a tapering cavity, the walls of which are at an angle of 39.5 with the centers of the benzene rings 6.67 A apart. The carbonyl groups of the glycoluril moiety, which are hydrogen-bond acceptor sites, are separated by 5.52 A. It was also possible to obtain a crystal structure of the chiral dibromo-derivative 4 of clip 3 (Fig. 3). This compound was separated into its enantiomers by HPLC on a chiral stationary phase [12]. 

A benzene solution (2.5 mL) of 4,4,5,5-tetramethoxy-2,7-dimcthylcyclohcpta-2,6-dicnonc (177 mg, 0.7 mmol) was irradiated through a Pyrex filter by means of a high-pressure Hg lamp for 1 h. The reaction mixture was purified by HPLC (Microporasil, FiOAc/hexane) to give 26 as colorless crystals yield 88.7 mg (50%) mp 69-70 C. 

More recently Okawara, Hotta and Shimura (48) hydrolyzed the more reactive dichlorodiethoxysilane in a benzene-pyridine mixture, isolated the corresponding linear dimer, tetramer, and pentamer, and obtained evidence for the presence of smaller amounts of the cyclic dimer, trimer and tetramer. The partial hydrolysis of tetramethoxy-, tetra-ethoxy-, tetra-n-butoxy- and tetra-iso-pentoxysilane in alcohol-water mixtures was studied by Takatani (83) and the following products isolated ... 

The methanolysis reaction of 15 in MeOH yields the tetramethoxy-substituted (bis)metallo-tetrasiloxane 16 as a brown oil, showing good solubility in n-pentane, diethylether and benzene. 

Boar et al. (116,117) established the 2-acetoxylation of enamides 405 by use of LTA oxidation (Scheme 54). Dorn et al. (118) applied the reaction to oxyprotoberberines to achieve the synthesis of ( )-l3)8-hydroxytetra-hydroprotoberberines, the key step being C-13 acetoxylation. LTA oxidation in benzene of CHiCL of 2,3-dimethoxy-, 2,3,10,11-tetramethoxy-, and 2,3-methylenedioxy-9, lO-dimethoxy-oxyprotober-berines (406,407, and 245) led to the corresponding 13-acetoxy-oxyprotober-berines 408, 409, and 410 in 62, 55, and 71% yield, respectively. Successive reduction of 409 and 410 with LAH and sodium borohydride gave ( )-13)3-hydroxyxylopinine (391) and ( )-ophiocarpine (411) in 60 and 52% yield, respectively (Scheme 54). 

Hydroxy-5,6,7-trimethoxyxanthone, which was isolated for the first time from H. ericoides, was successfully synthesized by Gil et aL [59]. The synthesis was performed from the new benzophenone precursor 25 (Fig. 13). Compound 25 was prepared by Friedel-Crafts acylation of 1, 3,4-tetramethoxy-benzene with 2,5-dibenzyloxybenzoic acid and oxalyl chloride. When benzophenone 25 was heated with Me4NOH, 5-benzoyloxy-2-hydroxy-2, 3, 4, 5 -tetramethoxybenzophenone (25) underwent cychzation to 2-benzyloxy-5,6,7-trimethoxyxanthone (26) [60]. Hydrogenolysis of this compound with H2/Pd-C [61] finally afforded 2-hydroxy-5,6,7-trimethoxyxanthone (27) which is identical to natural xanthone [60]. 

ISO standard 3527 shows character and data for this oil. Adulteration is done by turpentine oil or pure a-pinene, P pinene, and elemicin from elemi resinoid. l,2,3,4-Tetramethoxy-5-allyl benzene is... 

Obtained by reaction of 2,3-dimethoxy-benzoic acid with 1,2,3,5-tetramethoxy-benzene in trifluoroacetic anhydride for 23hatr.t. [1185]. m.p. and Spectra (NA) TLC [1185],... 

Obtained (poor yield) by reaction of 2,3,4, 5-tetramethoxy-benzoyl chloride with hydro-quinone dimethyl ether in benzene in the presence of aluminium chloride (16%) [1160]. 

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