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Diene group

Polymerization of compounds perfonned with UV light was first reported in the 1970s [86] and was followed by further studies [87, 88 and 89]. Another study was concerned with the deposition and polymerization of multilayers of alcohols and acids incoiyDorating the diene group, -CH=CH-CH=CH-, at the hydrophilic end of the molecule [90]. [Pg.2618]

The Diels-Alder Reaction usually occurs readily it is of great value (a) for diagnosing the presence of a conjugated diene grouping, (6) for synthetic purposes in the preparation of cyclic systems. [Pg.292]

Detergents containing a 1,3-diene group in the hydrophobic segment. Facile chemical modification by a Dieis-Aider reaction with hydrophiiic dienophiies in aqueous solution [69]... [Pg.197]

Benzo[fl]- (a), benzo[fc]- (b) and benzo[c]flnorenes (c) bearing a diene group (93) in spiro geometry are three possible combinatorial isomers wherein the direction of fnsion of the naphthalene is different (Fig. 15). The n reaction centers of the diene gronps are snbject to spiro-conjngation [98, 99, 102] with the planar aromatic n system. The effect of perturbation arising from spiro-conjngation on... [Pg.167]

Allene, Diacetylene and cis-trans-Diene Groupings. J. Amer. Chem. Soc. 75, 1372 (1953). [Pg.267]

Dienes bonded to silicones to give products stable to hydrolysis are available in a wide variety of combinations, from the distillable l,3-bis(isoprenyl)-l,l,3,3-tetramethyldisiloxane to high polymers with dozens of diene groups attached [23], Diels-Alder cycloadditions may be performed with dieno-philes. Maleic anhydride adds almost quantitatively to the conjugated diene system, giving easy access to a siloxane species of considerable industrial importance [24]. [Pg.259]

Furthermore, whenever the 1,3-diene group is not embedded in a rigid structure, e.g. in 612 and 713, it assumes the most stable s-trans conformation, just as in the case of 1,3-butadiene. Again dissymmetrically disposed substituents perturb the n —> it transition, which acquires some magnetic moment parallel to the electric one. [Pg.117]

Diastereoselective intermolecular nitrile oxide—olefin cycloaddition has been used in an enantioselective synthesis of the C(7)-C(24) segment 433 of the 24-membered natural lactone, macrolactin A 434 (471, 472). Two (carbonyl)iron moieties are instrumental for the stereoselective preparation of the C(8)-C(ii) E,Z-diene and the C(i5) and C(24) sp3 stereocenters. Also it is important to note that the (carbonyl)iron complexation serves to protect the C(8)-C(ii) and C(i6)-C(i9) diene groups during the reductive hydrolysis of an isoxazoline ring. [Pg.95]

Reductive elimination of an allylic diol group. A new synthesis of vitamin A involves reduction of the allylic diol 1, prepared in several steps from JJ-ionone, with a low valent titanium formed from TiCl3 and LiAlH, in the ratio 2 1. Thus, the allylic diol group of 1 [either (E) or (Z)] is reduced to an (E,E)-1,3-diene group to form the silyl ether (2) of vitamin A.1 When the primary hydroxyl group is protected as an acetate, the reduction gives a mixture of (E)- and (Z)-2. [Pg.307]

If the conjugated diene group is in the acyl chain of the acylcobalt carbonyl, then cyclization is possible. Thus, sorbylcobalt tricarbonyl triphenylphosphine on heating to 80°C., cyclizes to 2-methyl-7r-cyclopentenonylcobalt dicarbonyl triphenylphosphine (41). [Pg.191]

Conjugated dienes take part readily in triplet-sensitized photodimerization. and the products obtained from buta-1.3-diene (2.691 include a (4 + 2) adduct as well as slereoisomeric (2 + 2) adducts. The reaction is non-concerted. and a rationalization for the products is provided on the basisof the formation of a biradical intermediate as shown (which is the most stable of the three possible biradicals that might be formed in the first step), by the attack of triplet diene on ground-state diene. Cross-addition takes place in some systems, such as myrcene (2.70) where a triplet diene group attacks the alkene within the same molecule direct irradiation of myrcene gives mainly... [Pg.64]

Laschewsky and Ringsdorf [203J studied the deposition and polymerisation of multilayers of alcohols and acids incorporating the diene group, — CH=CH—CH=CH— at the hydrophilic end of the molecule. The carbon atoms in this group are conventionally labelled from 1 to 4 starting from the hydrophilic end. Ultraviolet absorption studies of the polymerisation process indicate that initial polymerisation probably links atoms 1 and 4 in adjacent molecules respectively, thus creating a new... [Pg.85]

Baikalosterol is a novel steroid with a 24-ethyl-26-nor-22,25-diene group in the side chain isolated from the sponge Baicalospongia bacilifera, a common species of the Baikal lake. [Pg.554]

The millable materials have a diene group (-CH=CH-) included in the polymer to allow for cross-linking by sulfur or by peroxides. However, the capital costs to use millable polyurethanes are high because rubber mills, presses, and heavy-duty molds are needed to produce an article. [Pg.272]

The Erythrina alkaloids are conveniently divided into two main structural groups the 1,6-diene group and the Al(6)-alkene group (see Fig. 1). The biogenetically important alkaloid erysodienone cannot be classified in this way. [Pg.2]

Hydroperoxides of linolenate decompose more readily than those of oleate and linoleate because active methylene groups are present. The active methylene groups are the ones located between a single double bond and a conjugated diene group. The hydrogen at this methylene group could readily be abstracted to form dihydroperoxides. The possibilities here for decomposition products are obviously more abundant than with oleate oxidation. [Pg.66]

The intramolecular Diels-Alder reaction promises to become widely used in the synthesis of natural products from reports of recent research (142-144). In natural alkaloid synthesis by a Diels-Alder reaction, an enamide was utilized as either a suitable dienophile or diene group. There exist numerous examples of bimolecular and intramolecular Diels-Alder reactions of enamides with various dienophiles as well as bimolecular (4 + 2) cycloadditions of enamines with electron-deficient dienes. On the other hand, there appear to be only few reports of the (4 + 2) cycloaddition reactions of enamides with unactivated dienes. [Pg.265]

Trienes are produced by treatment of the adducts with boron trifluoride85 87. However, the cycloaddition of 4-phenyl-3//-l,2,4-triazole-3,5(4//)-diones has been principally applied to protect steroidal 5,7-dienes allowing manipulation of other groups. The diene group is then... [Pg.985]

Cycloaddition of 4-phenyl-3//-l,2,4-triazole-3,5(4//)-dione to provitamin D3 affords exclusively the product formed by addition to the least hindered a-face of the more reactive diene, the structure was determined by X-ray8. The diastereoselectivity appears to be determined by the steric effect of the rran.v-hydrindane system, although the mechanism has not been elucidated. The cycloaddition of 4-phenyl-3//-l,2,4-triazole-3,5(4//)-dione was exploited to temporarily protect the diene group in the syntheses of la-hydroxy vitamin D3 7 a(X = H)8,9 and la,25-dihydroxy vitamin D3 7b (X = OH, starting from 25-hydroxy provitamin D3)10. Complete stereocontrol was observed in the cycloreversion step. For related cycloadditions to vitamin D3 see Section 7.2,10.3.4. [Pg.995]

The preparation, physico-chemical characterization and technolc cal evaluation of ethyleneqjropylene-based terpolymers containii pendant conjugate diene groups, which were nan EPTMs in analogy with EPDMs according to ASTM nc nen-clature have been described in detail in previous articies ... [Pg.6]

By contrast, OTl reacts incompletely, even at 150 °C. The blodc distribution of 2,4,6-octatriene in OTI seems the main reason for the incomplete reaction of the adjacent diene groups, because Bell observed largely incomplete reactions of poly-13,5 Jiexatriene with sewral dienophiles in particular, with bulky ones, more than 50% conversion was never achieved. In fact, severe steric constraints arise for a diene group belonging to a 1,6-triene homosequence wlwn the two adjacent Diels-Alder adducts are formed. [Pg.57]


See other pages where Diene group is mentioned: [Pg.34]    [Pg.49]    [Pg.1270]    [Pg.112]    [Pg.977]    [Pg.70]    [Pg.977]    [Pg.259]    [Pg.49]    [Pg.216]    [Pg.1854]    [Pg.266]    [Pg.8]    [Pg.153]    [Pg.118]    [Pg.127]    [Pg.313]    [Pg.4]    [Pg.49]    [Pg.1001]    [Pg.11]    [Pg.49]    [Pg.54]    [Pg.64]    [Pg.3305]    [Pg.4]   
See also in sourсe #XX -- [ Pg.85 ]




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2.4- Diaza-l,3-diene groups

Allenyl groups from dienes

Diene ester group

Dienes iron protecting groups

Protecting groups for dienes

Sulfinyl Group Containing Dienes and Dienophiles

Vinyl group, 39 dienes

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