2.3- Heptadien

The aggregation pheromone of the leaf beetle Diorhabda elongata Brulle (Coleoptera Chrysomelidae) have been identified as two compounds namely, (2E , 42 )-2,4-heptadienal and (2E , 42 )-2,4-heptadien-l-ol produced exclusively by males. They were also detected in trace quantities from females but the levels in males were 8—40 times higher. ... 

Eisen-Komplexe mit alkoholischer Hydroxy-Gruppe wie 1-Ferrocenyl-ethanol und (endo-6-Hydroxy-2,4-heptadien)-tricarbonyl-eisen kdnnen in einer Zweistufen-Reaktion durch O-Sulfonylierung zu den Methansulfonsaure-estern und anschlieBende Umsetzung mit sekundaren Aminen wie Dimethylamin in tertiare Amine umgewandelt werden [z.B. (l-Dimethylamino-ethylj-ferrocen und (6-Dimethylamino-2,4-heptadienJ-tricarbonyl-ei-serif. ... 

The mechanism of the cycloaddition appears to be concerted for various reagents however, for several cases, radical cation cycloaddition-cycloreversions have a stepwise component. For example, CIDNP effects observed during the PET induced dimerization of spiro[2.4]heptadiene (97) identify a dimer radical cation with spin density only on two carbons of the dienophile fragment this intermediate must be a doubly linked radical cation ( 99 + 282,283 pulsed laser experiment at high concentrations of 97 supports a second dimer radical cation at high... 

Raw potato possesses little aroma. Approximately 50 compounds have been reported to contribute to raw potato aroma. Raw potatoes have a high content of LOX, which catalyses the oxidation of unsaturated fatty acids into volatile degradation products (Scheme 7.2) [187]. These reactions occur as the cells are disrupted, e.g. during peeling or cutting. Freshly cut, raw potatoes contain ( ,Z)-2,4-decadienal, ( ,Z)-2,6-nonadienal, ( )-2-octenal and hexanal, which are all products of LOX-initiated reactions of unsaturated fatty acids [188,189]. It is reported that two compounds represent typical potato aroma in raw potato methional and ( ,Z)-2,6-nonadienal [189]. Other important volatiles in raw potatoes produced via the LOX pathway are l-penten-3-one, heptanal, 2-pen-tyl furan, 1-pentanol and ( , )-2,4-heptadienal [189]. Pyrazines such as 3-iso-propyl-2-methoxypyrazine could be responsible for the earthy aroma of potato [35]. Some of the most important character-impact compounds of raw potatoes are summarised in Table 7.8. Aroma compounds from cooked, fried and baked potatoes have previously been reviewed [35]. 

The dihydropyridazine (764) is unstable and loses nitrogen rapidly to yield a 1,3-diene (765) (69JA777, 72CC1260). Since (764) is generated by hydrolysis and oxidation of the cycloadduct (763) prepared from azodicarboxylate and2,4-hexadiene, it has proven possible to functionalize the double bond of (763) prior to nitrogen extrusion. Cyclopropanation, hydrolysis, decarboxylation and oxidation of (763) produce the 2,4-heptadiene (767) in a stereospecific manner via a concerted, orbital symmetry allowed retro-Diels-Alder process (Scheme 177). 

Diels-Alder cycloadditions of the readily available spiro[2.4]heptadiene (15) are a useful entry to spiro(cyclopropane-l,7 -norbornene) and related polycyclic compounds (equation 17)38. 1,1 -Diacetylcyclopropane was found to undergo unusual base catalyzed cyclizations resulting in spiroannulated cyclopropanes (equation 18)3,-4°. 

Exercise 21-22 Unlike the conversion of bicyclo[2.1,0]-2-pentene to 1,3-cyclo-pentadiene, bicyclo[4.1.0]-2,4-heptadiene is transformed to 1,3,5-cycloheptatriene very rapidly at low temperatures by what appears to be a wholly concerted mechanism. Account for this difference. 

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. 

Clausen et al. (2005) found many similarities between odorants emitted from linseed oil as well as from a floor oil made of this linseed oil, concluding that the odorants of the linseed oil are also responsible for the odor of the floor oil. Of the 139 listed perceived odorants only 45 were identified by GC—MS library search and retention characteristics. Important odorants with a high detection frequency were acetaldehyde, propanal, butanal, pentanal, 2-pentenal, hexanal, 2-hexenal, heptanal, 2-heptenal, 2,4-heptadienal, octanal, 2-octenal, nonanal, 2-nonenal, 2-decenal, benzaldehyde, l-penten-3-one, l-penten-3-ol, pentyl oxiran, acetic acid, propionic acid, butanoic acid, pentanoic acid, hexanoic acid, octanoic acid. 

However, only limited experimental evidence is available concerning the key step of the dimerization, i,e. the addition of the radical cation to the parent olefin. Does this addition occur stepwise or in concerted fashion Does the radical cation serve as a the diene component ([3 + 2]cycloaddition) or as dienophile ([4+ l]cy-cloaddition) The observed retention of dienophile stereochemistry and orbital symmetry arguments (Fig. 7) favor the [4 + l]cycloaddition type. Although it is difficult to distinguish the [3 + 2] from the [4 + l]addition type, a stepwise component for the cycloaddition and the complementary cycloreversion has been established in at least one system, viz., spiro[2.4]heptadiene. 

Aldehydes Hexanal, 2,4-Decadienal (EZ) Heptanal, 2,4-Decadienal (EE) 2-Nonenal, 2-Ethylhexenal 2-Hexenal, 2,4-Heptadienal 2-Undecenal, 2,4-Nonadienal 2-Heptenal, Nonanal, Decenal Decanal. 2-Octenal. Octanal CORC ++ Decadienal (EZDe) (RV = 0.991)... 

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