Trienes palladium complexes

Cross-conjugated trienes have attracted interest in polymer chemistry and theoretical chemistry as well as in synthetic chemistry.11 Although a palladium complex catalyzed 1,2-propadiene dimerization in the presence of water or an amine produced hydroxylated or aminated 2,3-dimethyl-2,3-butadiene,12 the method was not applied to the synthesis of cross-conjugated trienes. Another interesting feature... 

A novel triolefin ligand (E,E,E)-l,6,ll-tris[(2,4,6-triisopropylphenyl)sul-fonyl]-l,6,ll-triazacyclopentadeca-3,8,13-triene was anchored to a polystyrene support [47] (Scheme 9). Thus, the 15-membered triene 24 bearing a styrene group underwent polymerization with styrene and DVB to afford the cross-linked PS-supported cyclic triene 25. The supported macrocyclic triene 25 was treated with Pd(PPh3)4 to give the palladium complex 26. The complex... 

In the presence of in, V -generated palladium(O) species, an electrophilic 7t-allyl complex 228 is formed, which is readily engaged in an intramolecular carbometallation (Scheme 57). The resulting vinylpalladium species then undergoes a Stille-type cross-coupling to provide a triene.232... 

Equations 1 to 3 show some of fixation reactions of carbon dioxide. Equations la and lb present coupling reactions of CO2 with diene, triene, and alkyne affording lactone and similar molecules [2], in a process catalyzed by low valent transition metal compounds such as nickel(O) and palladium(O) complexes. Another interesting CO2 fixation reaction is copolymerization of CO2 and epoxide yielding polycarbonate (equation 2). This reaction is catalyzed by aluminum porphyrin and zinc diphenoxide [3],... 

A mixture of palladium chloride and triphenylphosphine effectively catalyzes carboxylation of linoleic and linolenic acids and their methyl esters with water at 110°-140°C and carbon monoxide at 4000 psig. The main products are 1,3-and 1,4-dicarboxy acids from dienes and tricarboxy acids from trienes. Other products include unsaturated monocar-boxy and dicarboxy acids, carbomethoxy esters, and substituted a,J3-unsaturated cyclic ketones. The mechanism postulated for dicarboxylation involves cyclic unsaturated acylr-PdCl-PhsP complexes. These intermediates control double bond isomerization and the position of the second carboxyl group. This mechanism is consistent with our finding of double bond isomerization in polyenes and not in monoenes. A 1,3-hydrogen shift process for double bond isomerization in polyenes is also consistent with the data. 

The new metallocarbene complex l,3-bis(2,6-diisopropylphcnyl)-4,5-dimethyl-3//-imidazolidenylpalladium(O) has been reported to catalyse the dimerization of butadiene in the presence of propan-2-ol to afford octa-l,3,7-triene, rather than the usual telomer-ization products, typical for other palladium catalysts. The new catalyst is characterized by an unprecedented efficiency (TON > 80000 and TOF > 5000 h 1)82... 

Coordination chemistry of (/i, E)-1,6,11 -tra( arenesulfonyl)-1,6,11 -triazacyclo-pentadeca-3,8,ll-trienes and the catalytic properties of their palladium metal complexes 04MI49. 

The following reactions of norbornene and other nonfunctionalized alkenes with substituted methylenecyclopropanes illustrate these points. (1-Methylethylidene)- and (diphenyl-methylene)cyclopropane (1 R = Me, Ph) give rise to the same type of cycloadducts in the presence of either nickel(O) or palladium(O) catalysts. Even at temperatures as low as 40 "C with bis(> -cycloocta-l,5-diene)nickel(0) as catalyst, 2 may be isolated in 70% yield. The reaction can be extended to vinylbenzene and ethene at temperatures of between 40 and 60 °C, where it may be advantageous to use (cyclododeca-l,3,5-triene)nickel(0) ° as a source of the catalytically active nickel(O) species instead of bis(j7" -cycloocta-l,5-diene)nickel(0). ° This is because ligand dissociation from the former complex is more facile, especially at relatively low temperatures. 

Since vinyl stannanes (chapter 18) couple with electrophiles under catalysis by Pd(0), it makes sense to create the electrophile by the palladium-catalysed reactions of allylic acetates in the same pot.50 The vinyl stannane 304 reacts cleanly with the more complex allylic acetate 305 with 0.2 equivalents of Pd(0) to give the triene 306 in good yield.51... 

Mechanistically, this reaction can be understood on the basis of the Jolly mechanism. As before, oxidative coupling affords the palladacycle 12, and protonation (adding Ha+ in an Se fashion) leads to the chelated 7r-allyl intermediate 13. In the absence of a good nucleophile, 13 loses proton Hb to afford a palladium(O) complex of the observed triene product (Scheme 4). It should be noted that the initially formed triene may subsequently undergo Pd-catalyzed double bond isomerization and thus in some cases product mixtures will be observed. 

Also trienes such as cyclododecatriene-1,5,9 yield mono- and dicarboxylic acid esters [488, 509]. Cyclododecane tricarboxylic acid esters are formed with bis-triphenyl phosphine palladium dichloride as catalyst [448]. The catalyst can be recycled [517]. Nearly quantitative syntheses of monocarboxylic acid esters of cyclododecadiene and of tricarboxylic acid esters of cyclododecane can be achieved with complex Pd-catalysts. 

After investigation of the palladium-catalyzed cascade cyclization/Suzuki coupling reactions of 1,6-enynes, Zhu and Zhang turned their attention to the analog 1,2,7-triene 333 for the synthesis of various functionalized five-membered cycles 334/335 [115] (Scheme 6.88). Oxidative addition of allyl hahides or carbonates to Pd(0) generates 7i-allylpalladium species 336, followed by intramolecular cycUzation to form vinylpalladium complex 337. Subsequent transmetallation with aryl boronic acids... 

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