Penta-l,4-diene

The Diels-Alder addition of unstable thiadiazoline 498 to 1,4,5,5-tetrafluorocyclo-penta-l,3-diene provided the corresponding 4-thia-2,6-diazatricyclo[5.2.1.0 2,6 ]dec-8-ene-3,5-dione, which upon hydrogenation and following irradiation gave l,4,7,7-tetrafluoro-2,3-diazabicyclo[2.2.1]hepta-2-ene (see Scheme 85) <2006JFC(127)688>. 

Close examination of Table 6 reveals several points of interest. The isomerization of 3-methylcyclobutene yields only diene with none of the cis-isomer. With the transition state suggested for the isomerization of cyclobutene, either isomer could be formed. However, the methyl group away from the ring rather than towards it, with less steric repulsion. 

A density functional theory computational approach has been used " to investigate the [1,5]-hydrogen shift in (z)-penta-l,3-diene. Ab initio calculations of the activation barriers to proton transfer in nitrogen derivatives have been computed and these values used to show that the proton transfer in pyrazole is formally a... 

Polymerization of penta-l,3-diene by 1,4-addition with an optically active catalyst gives an optically active polymer comprising configurational repeating units with predominantly one type of chirality centre. 

An equilibrium was observed between ( )-penta-l,3-diene (1) and the cyclobutane 2.8... 

Butadiene. The reaction of methylene with butadiene was studied by Frey44 under experimental conditions similar to those in the case of allene, except that lower pressures were required to avoid butadiene polymerization. Products formed by attack of methylene on the C—H bonds were cis and vinyl-cyclopropane resulting from addition of CH2 to the carbon-carbon double bond underwent collisional deactivation or isomerization to cyclopentene and C dienes, with the exception of isoprene. 

Seven stereoisomeric and regioisomeric vinyloxetans (384 to 390) were obtained on photoaddition of acetaldehyde to ( )- or (Z)-penta-l,3-diene.336 Other instances of [2 -I- 2] photoaddition of ketones to conjugated dienes have been described.337 Iminooxetans are similarly prepared by addition of carbonyl-containing compounds to ketenimines.338... 

Ab initio calculations of the ionic Diels-Alder reactions of tiiazoloisoquinolinium and tetramethoxycarbonylquinohzinium ions with electron-rich dienophiles have been reported.215 The 2++ 4-cycloadditions of arenediazonium ions with (T)-penta-l,3-diene, 2,3-dimethylbutadicnc, and ( )-2-methylpenta-l,3-diene produce dihydropyr-idazines and pyridazinium salts.216 The similarity approach has been applied to predict successfiilly the preferred regiochemistry of various types of pericyclic reaction including polar and semi-polar Diels-Alder and 2 + 2-cycloadditions.217... 

For conjugated dienes, the heat of hydrogenation is less than the sum for the individual double bonds. For example, fran.v-pcnta-1,3-dicne has a monosubstituted double bond like the one in pent-l-ene and a disubstituted double bond like the one in pent-2-ene. The sum of the heats of hydrogenation of pent-l-ene and pent-2-ene is —242 kJ (—57.7kcal), but the heat of hydrogenation of fra s-penta-l,3-diene is only —225 kJ/mol (—53.7 kcal/mol), showing that the conjugated diene has about 17 kJ/mol (4.0 kcal/mol) extra stability. 

Addition of the Danishefsky diene derivative (l ,3Z)-l-methoxy-2-methyl-3-[(trimethylsilyl)oxy]penta-l,3-diene 216 (Scheme 1.19), was shown by Mikami, Fukuzumi, and co-workers to proceed in a stepwise process,... 

A related example with 2-methoxy-6-methyl-benzoquinone and penta-l,3-dien-5-ol has been reported Gras, J.-L. Tetrahedron Lett. 1977, 4117... 

Similar conversions were reported with 1,2,3,4,5-pentamethylcyclopenta-l,3-diene, to give stereoselectively the ent/o-6-phenyl-e.vo-4-methyl isomer of pentamethylphenylbicy-clo[3.1.0]hex-2-ene with > 85% yield.Benzylidene transfer to (Z)- and ( )-penta-l,3-diene, isoprene and 2-chlorobuta-l,3-diene regioselectively occurred at the more electron-rich C-C double bond to give trans- and cw-phenylvinylcyclopropanes. The transjcis ratio ranged from 0.52 to 2.2. 

The dithio esters 48 (R = Me, Ph or OEt) are generated by treatment of the salts 47 with bases they are trapped as Diels-Alder adducts in the presence of dienes (equation 31). Penta-l,3-diene gave mainly the regioisomers 49 in this reaction (equation 32). ... 

Davies and co-workers [12, 35] have exploited one particular aspect of the asymmetric cyclopropanation of alkenes with vinyl diazoacetates, namely, application to substrates suitable for subsequent Cope rearrangement. Cyclopropanation of dienes with predominant cfs-1,2-divinyl diastereoselection makes possible subsequent facile [3,3]-sigmatropic rearrangement with entry to 1,4-cycloheptadienes or bicyclic dienes. Two such examples employing cyclopenta-diene and penta-l,3-diene as substrates and the rhodium(II) prolinate catalyst, Rh2(2S-TBSP)4 in Fig. 1, are shown in Eq. (6) and Eq. (7),respectively cfs-l,2-di-vinylcyclopropanes are presumed to be intermediates in these annulation reactions. In contrast, ethyl diazoacetate and styrene with the prolinate catalyst (Fig. 

In contrast with their behaviour on heating, cis- and fra/w-penta-l, 3-dienes produce the 1,4-addition products cis- and trans- Me3SnCH2C= CHEt on photolysis in Me3SnH.502 No products arising from Sn—C bond rupture could be observed after irradiation of 2-trimethylstannylbuta-1,3-diene, and the main products found were the isomers (81)—(83).603... 

Vinylcyclopropane is converted to (3ii)-penta-l,3-diene and 2-methylbuta-1,3-diene by catalytic quantities of [RhCl(CO)2]2- Its homolog, 2-cyclopropylpropene, is similarly converted to (3ii)-2-methylpenta-l,3-diene and 2,3-dimethylbuta-1,3-diene. Although the same catalyst converts either ( )- or (Z)-l-methyl-2-phenylcyclopropane to identical mixtures of l-phenyl-2-methylpropene and l-phenylbut-2-ene, the reactions proceed at different rates. It has been proposed that ring opening and rhodium coordination to C-1 occurs first, followed by hydride migration to form the products. 

A. P. Mishchenko, V. M. Gryaznov, M. E. Sarylova, Effect of thermodifftision and chemical treatment of the surface of membrane catalysts made from palladium alloys with ruthenium and rhodium on penta-l,3-diene hydrogenation. Bull. Acad. Sci. USSR 1991, 40(6 (1)), 1154-1157. 

Arene Additions.—Evidence has been provided for the production of cyclobutadiene in the photolysis of (330) in solution the products isolated are dimethyl phthalate and syn-tricyclo[4,2,0,0 ]octa-3,7-diene. Thus, irradiation of(330) in the presence of either cis- or trans-penta-l,3-diene gave the above products and the Diels-Alder... 

Trityl tetrafluoroborate eliminates H" from tricarbonyl(cw-penta-l,3-diene)iron to furnish a dienyl complex [equation (8.56)]. 

Unsaturated polymers, particularly of dienic monomers, undergo a number of interesting thermal rearrangements under non-pyrolytic conditions. Golub has studied these reactions in some detail and has recently reviewed the subject. In the past two years accounts of thermal rearrangements of l,2-poly(hexa-l,4-diene)s and l,2-poly(/ra 5-penta-l,3-diene) have appeared. The former polymers have a predominantly 1,8-diene structure and cyclize mainly by a [2 + 2] or type II mechanism accompanied by a small amount of a type III reaction (Scheme 24). The latter is more important in the trans-, A- than in the cir-1,4-isomer. The first unambiguous example of a type III reaction was provided by the polymer of penta-1,3-diene. Scheme 25 shows a macromolecular... 

C10H18 2-tert-butyl-4-methyl-penta-l,3-diene 1115-18-0... 

How can you account for the fact that cis-penta-l,3-diene is much less reactive than frans-penta-l,3-diene in the Diels-Alder reaction ... 

Some aliphatic, alicyclic and aromatic hydrocarbons may be products of oxidation and degradation of substances other than lipids for example, penta-l,3-diene arises by decarboxylation of sorbic acid (see Section 11.2.1.1.2), which is used as a preservative. 

Some microorganisms (such as Penicillium roqueforti) decar-boxylate sorbic acid to penta-l,3-diene, which causes an off-flavour (resembling kerosene) in cheeses (Figure 11.1). The threshold concentration of penta-1,3-diene is 1 mg/kg. Also reported are cases of contaminated margarines, fruit drinks, jams and marzipan, and similar products that used pure cultures of microbial strains (such as blue cheese and fermented dairy products). 

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