Trans-1,3-Pentadiene

It was also shown that a cahonic allylnickel complex [(q3-crotyl)Ni P(OEt)3 2]PF6 catalyzes this reaction without added acid and that ds- and trans-1,3-pentadienes react with morpholine to give a mixture of 1,2- and 1,4-addition products [178]. 

The polymerization of trans-1,3-pentadiene, 149, in a chiral channel inclusion complex with enantiomerically pure perhydrotriphenylene affords an optically active polymer, 150 (236). Asymmetric polymerization of this monomer guest occurs also in deoxycholic acid inclusion complexes (237). 

It is noteworthy that, at variance with bromination and chlorination which generally occur without isomerization of the disubstituted double bond, fluorine addition to the 1,2-bond of cis- and trans-1,3-pentadienes gives mainly the trans-adduct 13, besides smaller amounts of compounds 14-16 (equation 24). 

Later on, product distribution studies15 of the ionic addition of chlorine to conjugated dienes, and in particular to cyclopentadiene, 1,3-cyclohexadiene, cis,cis-, trans,trans-and c ,fraws-2,4-hexadienes, and cis- and trans-1,3-pentadienes have supplied the first stereochemical data, showing that the stereochemistry of 1,4-addition is predominantly syn, although to an extent smaller than that of bromine addition. Moreover, the 1,2-addition is generally non stereoselective, except for the addition to the 3,4-bond of cis-and trans-1,3-pentadienes where the attack is 89-95% anti. Finally, appreciable amounts of cis- 1,2-dichlorides were obtained from the two cyclic dienes, whereas 2,4-hexadienes showed a preference for anti 1,2-addition, at least in the less polar solvents (carbon tetrachloride and pentane). On the basis of all these results the mechanism shown in equation 29 was proposed. 

Figure 19.7. Cyclic batch elution chromatography obtaining high product purity and high throughput by using incomplete resolution (overlapping bands) and recycling the mixed fraction (mf) to the feedstock (a) Control of band separation and cut points determines fractional impurities t mij mr and Ami /mr2-<4l)> (b) Chromatogram for separation of pure ds- and trans- 1,3-pentadiene. Components 1, isoprene 2, trans- 1,3-pentadiene 3, cis-l,3-pentadiene 4, cyclo-pentadiene. Component 1 is eluted at almost the same time as component 4 of the...

SCHEME 110. Fe-catalyzed codimerization of isoprene and trans-1,3-pentadiene. 

An iron catalyst formed from a C2-symmetric l,4-diaza-l,3-diene-FeCl2 complex and an organomagnesium compound promotes the cyclo-codimerization of isoprene and trans-1,3-pentadiene to give 1,7-di-methyl-1,5-cyclooctadiene in a fair ee (Scheme 110) (270). 

Certain chiral organic compounds create crystalline environments and act as enantio-controlling media (7) even though they do not function as true catalysts. Natta s asymmetric reaction of prochiral trans-1,3-pentadiene, which was included in the crystal lattice of chiral perhydro-triphenylene as a host compound, to form an optically active, isotactic polymer on 7-ray irradiation, is a classic example of such a chiral molecular lattice (Scheme 1) (2). Weak van der Waals forces cause a geometric arrangement of the diene monomer that favors one of the possible enantiomeric sequences. 

Ahnliche Untersuchungen wurden am trans-1,3-Pentadien (XCIX) beschrieben (196). Mit einem Katalysator aus (+)-Tri(2-methylbutyl)-aluminium und Titantetrabutylat entsteht ein inaktives Polymeres. Dagegen wurde mit dem System Triathylaluminium und (—)-Titantetra-menthylat eine betrachtliche optische Aktivitat erzielt. Die Polymeren wurden fraktioniert der Anteil mit dem hochsten cis-l,4-Gehalt wies auch die hochste optische Aktivitat auf. Bei der Ozonolyse dieser Polymeren wurde optisch aktive Methylbernsteinsaure erhalten damit ist bewiesen, daB die optische Aktivitat des Polymeren von asymmetrischen C-Atomen der Polymerkette herruhrt. 

Natta, Porri and co-workers have studied the stereospecific polymerization of trans 1.3-pentadiene (51,52,53,54,55). This monomer acts as a propylene vinylogue in 1.2-polymerization. It requires a cationic catalyst such as alkylaluminum dichloride to produce the 1.2 polymer. 

Fig. 7. Anionic catalysts and their effectiveness for the steric control in the polymerization of butadiene and isoprene. Cationic catalysts in the polymerization of trans- 1.3-pentadiene...

The 1,4 polymerization of trans-1.3-pentadiene has been studied by Natta, Porri and coworkers. Their results also show that the cis polymerization occurs with catalysts of ionicities in the middle region, while the trans structures come in the more ionic regions. The methyl group at the end of the diene systems shifts the transition points... 

I, 3-diene polymerization. Monomer molecules are included in chiral channels in the matrix crystals, and the polymerization takes place in chiral environment. The y-ray irradiation polymerization of trans- 1,3-pentadiene included in 13 gives an optically active isotactic polymer with a trans-structure. The polymerization of (Z)-2-methyl-1,3-butadiene using 15 as a matrix leads to a polymer having an optical purity of the main-chain chiral centers of 36% [47]. 

When PhMn(CO)s reacts with trans-1,3-pentadiene, and the resulting acyl substituted derivative 68 heated to 120°C (0.1 mm Hg), loss of carbon monoxide leads to a 73% yields of 69 [Eq. (32)] (226). Recently a derivative 70 of the parent ligand has been prepared from (Ph3P)2ReH7 and furan under reflux in thf, in the presence of 3,3 -dimethyl-1-butene as hydrogen acceptor (227). 

However, as the temperature rises this is rapidly converted to the TT-allylic complex. Similar complexes of conjugated dienes involving complexing of only one double bond have been observed with trans-1,3-pentadiene, cis,trans-2, i-hexadiene, and 1,3-cyclooctadiene. 

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