1.5- dienes preparation

The 1,4 units constitute somewhat less than half of the total in polymerized dienes prepared by anionic polymerization at moderate temperature. Their proportion increases with the polymerization temperature. 

Toshima N, Yonezawa T, Harada M, Asakuara K, Iwasawa Y (1990) The polymer-protected Pd-Pt bimetallic clusters having catalytic activity for selective hydrogenation of diene. Preparation and EXAFS investigation on the structure. Chem Lett 19 815-818... 

Figure 4. 13C-NMR spectrum of a CDCls solution of poly(5-methyl-1,4-hexa-diene) prepared with a EtgAlCl/S-TiCl, catalyst at 0°C in pentane solvent, ambient temperature. Reproduced, with permission from Ref. 13, Copyright 1979, American Institute of Physics.

Backvall and Juntunen and Fuchs and Braish have developed ( )-2-phenylsuphonyl-1,3-dienes prepared under Julia conditions as versatile synthones for a variety of organic transformations103. These dienes undergo facile Diels-Alder reaction and subsequent 1,4-elimination of sulphinic acid by base to generate a new diene (equation 62)103a. An elegant extension of this method is to use chiral sulfinylmaleate which, on Diels-Alder... 

Figure 9.3. Dienes prepared by acetylene coupling reaction.

Ketenes, which are even more reactive than isocyanates, afford ketenimines at or below room temperature [62CRV247 84JOC2688 89JCS(P1)2140]. At elevated temperatures, dimerization or polymerization occurs (21HCA887). Although N-aryl- and A-vinyliminophosphoranes react smoothly with ketenes, strong acceptor substituents on the nitrogen hamper the reaction thus V-acyliminophosphoranes do not react with ketenes. Vinylketenimines such as 2-aza-l,3-dienes prepared in this way from... 

Another approach to synthesize stable Diels-Alder adducts of Cjq was introduced by Mullen and co-workers [41—43], The use of o-quinodimefhane derivatives as dienes, prepared in situ, leads to the formation of thermally stable cycloadducts (Scheme 4.5). As with the isobenzofuran addition product [13], a cycloreversion of these adducts would need to overcome the stabilization provided by the aromatic system and would also give the unstable o-quinodimefhane intermediate. A fast ring inversion, at elevated temperatures, of the cyclohexane moiety causes a 2 -symmetry of the cycloadduct, leading to 17 lines for the fuUerenyl carbons in the NMR spectra [41]. 

Absorption and Deposition of CLA in Animal Tissues. Miller etal (27) described a method employing the methyl ester of conjugated dienes prepared from com oil as tracers of fat metabolism. It was postulated that the conjugated dienoic isomers could be differentiated from other fatty acids in body fat by spectrophotometric absorbance at 233 nm. 

Extrusion of S02 provides a unique opportunity for diene preparation Because of the sulfoxide influence, substitution at these positions quite easy. 

This diene, prepared according to A. E. Montagna and D. H. Hirsch fUS Patent 2,902,722 (1959)], is practically a pure nms isomer, whereas the commercially available reagent is a cis-frans-isomer mixture. 

Disilabicyclo[2.2.2]octa-2,5-dienes, prepared by the interaction of the radical anion of anthracene, naphthalene or biphenyl with 1,2-dichlorotetra-methyldisilane were found to undergo thermal decomposition472). 

Tellurabicyclo[3.3. l]nona-2,6-diene, prepared from sodium tclluride and 1,5-dibromoocta-2,6-diene, lost tellurium when heated at 175° in toluene in a sealed tube giving bicyclo[5.1.0]octa-2,5-diene1. 

Dienamides (133) readily undergo intermolecular [4 + 2] cycloadditions, as exemplified by the highly emfo-selective reaction of (136) with maleic anhydride giving (137) (Scheme However, the main advantage of the simple diene preparation (131) — (133) is the facile introduction of an alkenic chain. 

The formation of the amine (496) when 3)5-toluene-p-sulphonates are treated with 2-dimethylaminoethanol involves both inversion at C-3 and demethyla-tion. The reaction of androstane-16,17-ketols and 17 -acetoxy-16a,Ha-epoxide with morpholine to give a-morpholino-ketones has been thoroughly investigated and rationalised. H/5-Aminoandrosta-3,5-diene, prepared by reduction of the H-oxime, possesses some antimicrobial activity which is not enhanced by substitution of the amino-groups with 2-chloroethyl, 2-hydroxy-ethyl, or 3-aminopropyl groups similar 2-chloroethyl substituted H)5-amines have been cyclised by treatment with base to give H -aziridines. All four... 

The enantiomers of 2-cyclohexy(-2-hydroxy acetic add 12 and their esters are conveniently obtained from the corresponding mandelic adds (or derivatives) by catalytic hydrogenation with a platinum catalyst16 17. The methyl ester has been used for the enantioselectivc protonation of lactone enolates (Section D.2.1.) and the chiral diene prepared analogously to the O-methylmandclic acid derivatives11-13 described in the preceding section in diastereoselective Diels-Alder reactions (Section D. 1.6.1.1.1.). 

Alkadienes, 372-390. See also Dienes preparation of, 378-379 relative stabilities, 374-375 ultraviolet-visible spectra, 524—526 Alkaloids, 869 Alkanes, 53-88... 

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