3.6- Dimethyl-2,4-heptadiene

PP and a-PP decomposed into a large number of aliphatic compounds without a residue. Some 96 wt% of the carbon in PP and 97 wt% of the carbon in a-PP was converted to volatile organic compounds such as alkanes, alkenes and dienes. Major compounds are, for instance, C9 hydrocarbons, such as 2-methyl-1-octene, 2-methyl-2-octene, 2-methyl-4-octene, 2,4-dimethyl-l-heptene and 2,6-dimethyl-2,4-heptadiene. 

Phoronediozonide (Sym-Diisopropylideneacetone-ozonide). C j 407, light green syrup, very expl, self-flammable on standing in air. Was prepd by Harries Turk by passing ozone thru a well cooled chloroformic soln of phorone [2,4-dimethyl-heptadien-(2,5)-on-(4)], (CH3)2C CH.CO,CH C(CH3)2, followed by vacuum removal of chlf at 20°... 

Hydroxy-3 -methyl-3-[4-methyl-pentcn-(3)-yl]-2-[2,6-dimethyl-heptadien-(l,5)-yl]- 660... 

Phorone (Di iso p ropy lidene acetone, 2,6-dimethyl-2,5-heptadien-4-one). 

Valence Isomerization of the 2-Thiabicyclo[3.2.0]heptadiene Moiety In principle, a valence isomerization of thiabicyclo[3.2.0]heptadiene skeleton would lead to a thiepin ring system. Wynberg et al. 23) reported that the photochemical adduct (28) from benzo[6]thiophene and dimethyl acetylenedicarboxylate was not thermally stable. When heated in diglyme, it loses sulfur to give dimethyl 1,2-naphthalenedicarboxylate. This reaction presumably proceeds via ring opening of 28 to 2,3-dimethoxycarbonylbenzo[6]thiepin (29) which readily eliminates sulfur. This synthetic route was successfully applied to the reaction of electron-deficient acetylenes with enamines of 2,3-dihydrobenzo[fe]thiophen-3-ones in which the enamine moiety constitutes part of a thiophene system. When 3-pyrrolidin-l-yl-benzo[6]thiophene (30) was allowed to react with dimethyl acetylenedicarboxylate... 

Reinhoudt et al.53) have reported the first synthesis of a monocyclic thiepin stabilized by electronic effects of the substituents. This synthesis utilizes the idea described in Section 2.3.3. 3-Methyl-4-pyrrolidinothiophene (85a) was treated in deuteriochloroform at —30 °C with dimethyl acetylenedicarboxylate. H-NMR monitoring of the reaction indicated that a [2 + 2]cycloaddition proceeded slowly at this temperature giving the 2-thiabicyclo[3.2.0]heptadiene (86a) which rearranged via ring opening of the cyclobutene moiety to the 4-pyrrolydinylthiepin (87a). At the... 

Dimethyl-2,5-dihydrothiophene-2,5-endoperoxide, 2387 2,6-Dimethyl-2,5-heptadien-4-one diozonide, 3176... 

Ethylcyclop entanon e 3-Pentyl cyclopentanone 6-Methyl-3,5-heptadien-2-one 6-Methyl-2-cyclohexen-l-one 2,3-Dihydrocarvone Unidentified dimethylacetophenone 2-Butyrylfuran Dimethyl disulfide 2,6-Dimethylpyridine Isobutylbenzene Unidentified acetal (mol mass 154) Isobutyronitrile... 

Attempted esterification of the 7-azabicyclo[2.2.1]heptadiene-2,3-dicarboxylic acids (5) and (10) with diazomethane in mild conditions led to decomposition liberating the corresponding pjnroles. Dimethyl acetylenedicarboxylate, the other decomposition product, reacted further with an excess of diazomethane to give dimethyl pyrazole-4,5-dicarboxylate and an A-methyl derivative. ... 

In the 7-azabicyclo[2.2.1]heptadiene series there is as yet no instance known of aromatization by deamination such as occurs with some naphthalen-l,4-imine and anthracen-9,10-imine derivatives (see Sections III, H and IV, D). On the other hand, a close parallel exists between those reactions and some instances of aromatization of bicyclo[2.2.1] structures by loss of a heavier heteroatom from the 7-position, e.g., 70 71. 1,2,3,4,5-Pentaphenylphosphole reacts with dimethyl acetyl-... 

A different mode of cycloaddition occurs with 7-azabicyclo[2.2.1]-heptadiene derivatives, in which the nucleophilicity of the nitrogen atom determines the point of attachment of the electrophilic dienophile. The addition depicted in 87, which may occur in two steps via a zwitterionic intermediate rather than by a concerted mechanism, accounts for the structures (88) of 1 2 adducts obtained with A-methyl- or A-benzyl-pyrrole and dimethyl acetylenedicarboxylate. At a higher temperature the reaction with A-methylpyrrole also afforded the indole tetraester... 

Thiatriazoles are generally not characterized by cycloaddition reactions. Neunhoeffer et al. were not able to induce a reaction between 5-phenyl-1,2,3,4-thiatriazole (7) and 1,2-diphenylacetylene or dimethyl acetylenedicarboxylate (36) even at 12 kbar <85LA1732>. Similar negative results are reported with other reagents (see Section 4.19.4.1). However, a reaction between 7V,A-diethyl-l-propynylamine (40) and 5-phenyl-1,2,3,4-thiatriazole (7) took place at 12 kbar and a compound assigned structure (41) on the basis of MS and NMR was isolated in 17% yield. The suggested reaction pathway, initiated by a 1,3-dipolar cycloaddition reaction at N(2) and N(4) is shown in Scheme 5. Formation of an alternative triazabicyclo[2.2.1]heptadiene was left open. 

Die waBrig-alkalische Ringspaltung von 1,1,2-Trimethyl- bzw. l,l-Dimethyl-2-ethyl-1,2,3,6-tetrahydro-pyridinium-jodid fuhrt in guten Ausbeuten zu 1 -Dimethylamino-(2Z,4E)-hexadien (65%) bzw. l-Dimethylamino-(2Z,4E)-heptadien (64%)2 ... 

Tandem addition of trimethyltin followed by cyclization in a 1,6-heptadiene system [Eq, (7)] proceeds with surprising efficiency [30]. Oxidative destannylation of the primary product gives a synthetically useful dimethyl acetal. An acetylene-terminated tandem addition is shown in Eq. (8) [31]. 

Preparation of 3,5-dimethyl-4-(trifluoromethyl)-2,5-heptadien-4-ol. A 1-L, three-necked, round-bottomed flask, equipped with a reflux condenser, a magnetic stir bar and an addition funnel is flame dried under an atmosphere of argon. After the apparatus has cooled, 350 mL of anhydrous diethyl ether (freshly distilled from sodium benzophenone10 under argon) is added. Lithium wire (6.9 g, 1.0 mol, 3.2-mm diameter, 0.01% Na content, Aldrich Chem. Co., Milwaukee, WI), which is cut into 5- to 10-mm pieces and washed with hexanes, is added to the flask under a counterstream of argon gas. The reaction flask is cooled to 0°C in an ice bath and 68.9 g (0.51 mol) of 2-bromo-cis-2-butene (prepared in the previous step9) in 50 mL of anhydrous diethyl ether is added dropwise over a 45-min period while the reaction mixture is stirred. The reaction solution becomes cloudy due to the formation of lithium bromide. Stirring is continued for an additional 1.5-2 h at 0°C. 

Acid Catalyzed. Although ketonic carbonyl groups are less reactive than aldehydic carbonyls in the presence of basic catalysts, this is not the case with acid catalysts. Thus acetone undergoes aldol addition in the presence of sulfuric acid to give mesityl oxide, which then condenses with a third molecule of acetone to give a mixture ofphorone (2,6-dimethyl-2,6-heptadien-4-one) and mesitylene (1,3,5-trimethylbenzene). Ketones also condense with activated aromatic products in the presence of sulfuric acid to give coupled aromatic products. For example, acetone and phenol condense to bisphenol A (4,4 -isopropylidenediphenol), which is used in the manufacture of epoxy resins (qv) and polycarbonates (qv). 

Industrially, a selectivity to DAA of between 90—95% can be achieved (64). The principal by-products are mesityl oxide and acetone trimers. j W-Triacetone dialcohol [3682-91-5] can form by condensation of acetone with diacetone alcohol (116). Dehydration of ry/ -triacetone dialcohol can yield semiphorone [5857-71-6] (6-hydroxy-2,6-dimethyl-2-hepten-4-one), which may in turn ring close to form 2,2,6,6-tetramethyl-y-pyrone [1197-66-6/, or ultimately dehydrate to phorone [504-20-1] (2,6-dimethyl-2,5-heptadien-4-one) (146). Similarly, an unsymmetrical acetone trimer can also be formed which dehydrates to 2,4-dimethyl-2,4-heptadiene-6-one. These impurities complicate the high purity recovery of DAA, and are thought to be responsible for a yellow discoloration of DAA. The addition of dibasic acid (147) or nitrogen containing carboxylic or phosphonic acids (148) has been patented as refined product stabilizing agents. 

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