Dihydro-3,5-dimethyl

A number of alkaloids in this group differ from each other only in the number of methyl groups on the basic nitrogen. They were fully methylated where necessary by the formaldehyde-hydrogen catalytic reduction (Pd/C) and thus identified with the A,A-dimethyl bases, also reduced at the double bond. In this manner mucronine-B (50) and mucronine-H (55) yielded dihycLromucronine-A while abyssenine-A gave dihydromucronine-C. abyssenine-B and -C as well as mucronine-E and -F provided identical A, A-dimethyl dihydro derivatives. 

The 2,4-dihydroxy-3,3-dimethyl-butironitrile was treated hydrochloric acid and D,L-3-hydroxy-4,4-dimethyl-dihydro-furan-2-one (D,L-pantolacton) was obtained. The racemic mixture of D- and L-pantolactons was a division of D-and L- isomers by the adding of a-phenylethylamine. So D-pantolacton was isolated. 

Tautomerism of tetrazines was investigated by ID 15N INADEQUATE.85 Dimethyl dihydro-1,2,4,5-tetrazine-3,6-dicarboxylate can exist either in 1,2- (8) or... 

Borat (Bis-[ammoniak]-dime-thylboretio)-Dimethyl-dihydro-XIII/3b, 818... 

C. Dimethyl dihydro-1,2,4,5-tetrazine-3,6-dicarboxyiate. Absolute methanol (700 mL, Note 4) is placed in a dry, 2-L, round-bottomed flask fitted with an overhead stirrer, thermometer, and a 100-mL addition funnel and is cooled to -30 C. Thionyl... 

With perylene, one might have expected either the C-3/C-q dimethyl dihydro isomer, in analogy to the known chemistry of naphthalene, or the C-2/C-3 dimethyl dihydro isomer because of steric constraints at C-q. Yet, the C-l/C-q dimethyl dihydro isomer was obtained overwhelmingly. This result is in accord with the prediction of Minsky et al. (10) that C-l bears the highest electron density (and once C-l picks up an alkyl group in the quench, only one regioisomer can be made). 

Curiously, in reacting with methyl iodide so readily to make dimethyl dihydro products, the perylene dianion is distinct from the radical anion of naphthalene, which primarily reduces methyl iodide to the methyl radical and the iodide anion. 

Derivatives A/,A/-Dimethyl-dihydro-abyssinine-C = A/-Methyl-dihydro-abyssinlne-B (132) A/-Acetyl-abysslnine-C (132)... 

Tn thybham8aure 26 II304. 3.7.9 Tri thyl>hamsauie 2 533, II 304. 3.7>Pimethyl-l butyl hani8 ure 26 II304. 2.6>Di thoxy-8-oxo-7.9-dimethyl-dihydros parin 26, 548. 

In another paper, Mehrabzadeh et al. measured the oxygen and toluene permeabilities of the exfoliated HDPE/modified clay with dimethyl-dihydro-genated tallow-quatemary ammonium nanocomposites. It was found that by addition of 5 wt.% clay the oxygen and toluene permeability was reduced by 61.5% and 48% respectively. 

Dienes can also be used ia Friedel-Crafts cyclo alkylations. For example, treatment of phenol with 2,5-dimethyl-2,4 hexadiene gives 5,5,8,8-tetramethyl,6,7-dihydro-2-naphthol. 

Dimethipin. 2,3-Dihydro-5,6-dimethyl-l,4-dithiin-l,l,4,4-tetraoxide [55290-64-7] (dimethipin, oxidimetbiin, UBI-N252, Harvard) (25) is used as a cotton defoHant and has been used as an experimental desiccant in potato vines. In addition, it defoHates nursery stock, grapes, dry beans, and natural mbber and is used as a desiccant for seed of canola, flax (l lnum usitatlssimum), rice, and sunflower (He/lanthus annuus) (10). The product has been available since the mid-1970s and the experimental work was first reported in 1974 (44). 

Phenyl-3,6-dihydro-l,3,4-oxadiazin-2-one (50) is a high temperature blowing agent used primarily for polycarbonates (qv). It is prepared by the reaction of a-hydroxyacetophenone and methyl carbazate (52), made from hydrazine and dimethyl carbonate (175) ... 

Of the three benzenetricarboxyhc acids, only trimellitic acid as the anhydride is commercially produced in large volume, by Hquid-phase air oxidation of either pseudocumene or dimethyl benzaldehyde. The pseudocumene oxidation is another variant of the cobalt—manganese—bromine catalyst in acetic acid solvent as described in the terephthaUc acid section. The acid is available as a laboratory chemical (99). The lUPAC name of trimellitic anhydride is 5-isobenzofurancarboxyhc acid (l,3-dihydro-l,3-dioxo). 

Pentoxifylline is stmcturaHy related to other methylxanthine derivatives such as caffeine [58-02-2] (1,3,7-trimethylxanthine), theobromine [83-67-0] (3,7-dimethylxanthine), and theophylline [58-55-9] (3,7-dihydro-1,3-dimethyl-1 H-piirine-2,6-dione or 1,3-dimethylxanthine), which also show radioprotective activity in some instances, suggesting that methylxanthines as a dmg class may radioprotect through a common mechanism (see Alkaloids). In a retrospective analysis of cervical and endometrial cancer patients receiving primary or adjuvant XRT, no association between caffeine consumption and incidence of acute radiation effects has been found. However, there was a decreased incidence of severe late radiation injury in cervical cancer patients who consumed higher levels of caffeine at the time of thek XRT (121). The observed lack of correlation between caffeine consumption and acute radiation effects is consistent with laboratory investigations using pentoxifylline. 

In some instances a carbon-carbon bond can be formed with C-nucleophiles. For example, 3-carboxamido-6-methylpyridazine is produced from 3-iodo-6-methylpyridazine by treatment with potassium cyanide in aqueous ethanol and l,3-dimethyl-6-oxo-l,6-dihydro-pyridazine-4-carboxylic acid from 4-chloro-l,3-dimethylpyridazin-6-(lH)-one by reaction with a mixture of cuprous chloride and potassium cyanide. Chloro-substituted pyridazines react with Grignard reagents. For example, 3,4,6-trichloropyridazine reacts with f-butyl-magnesium chloride to give 4-t-butyl-3,5,6-trichloro-l,4-dihydropyridazine (120) and 4,5-di-t-butyl-3,6-dichloro-l,4-dihydropyridazine (121) and both are converted into 4-t-butyl-3,6-dichloropyridazine (122 Scheme 38). 

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