Esters diene dimerization

Catalyst Adducts Solvent Temp. 1°C] (time [h]) Yield [%] (based on butadiene) Lactones Esters Buta- Ref. diene dimers ... 

B.iii. Intermolecular Diene Dimerization Influence of Ester Substituents... 

When a bidentate phosphine is used as a ligand for the reaction of J-keto esters or /i-diketones, no dimerization takes place. Only a 2-butenyl group is introduced to give 68[49,62], Substituted dienes such as isoprene, 1,3-cyclohexa-diene, and ocimene react with carbon nucleophiles to give a mixture of possible regio- and stereoisomers of 1 1 adducts when dppp is used as a ligand[63,64]. 

Photochemical reaction of the ester 114 afforded the alkene 115 and three products derived from 115. A mechanism, involving dimerization of 114 leading to a dithietane intermediate 116, was proposed. Trapping of active sulfur species, generated from 116, with dienes was also described (75CB630). 

X(A1C13) = 0.5) to immobilize a ruthenium carbene complex for biphasic ADMET polymerization of an acyclic diene ester (Figure 7.4-2). The reaction is an equilibrium processes, and so removal of ethylene drives the equilibrium towards the products. The reaction proceeds readily at ambient temperatures, producing mostly polymeric materials but also 10 % dimeric material. 

A classic example is the dimerization of methyl cyclopentadienylcarboxylate (37) to Thiele s ester (38)67. Although diene 37b should be more reactive than 37c according to the FMO theory, it was diene 37c that reacted with diene 37b (equation 17). 

While linear dimerization of dienoic esters can also be accomplished with nickel-AMP systems, other functionalized dienes undergo little or no conversion. The reaction of methyl hexa-2,4-dienoate, 81, furnishes diastereomeric trienoic diesters (82) in high yields (equation 43). 

A typical example for type 1 is the dimerization of electron-rich olefins like aryl olefins, enol ethers, enol acetates, conjugated dienes, or enamino esters [39] ... 

Photolysis (> 290 nm) induced quantitative conversion of (20c and d) to the crystalline 3-azaquadricyclanes (22c and d) that isomerize in solution at 20° to the azepines (23c and d) at measurable rates. The azepines rapidly dimerize. The thermally forbidden 47 reversal of 22 to 20 was not observed.80 Prinzbach and Eberbach81 have carried out numerous cycloadditions and acid-catalyzed rearrangements of 22c and d and of 23c and d. The 3-azaquadricyclanes 22 have diene properties but, as valence isomerization to azepines is so easy (above), cycloadditions were achieved only with the very reactive dienophiles DMAD and EP. Reactions with 22c and d at -15° to - 30° over 24 to 48 hours using a large excess of ester gave 24 (R = H or E). If equimolecular proportions of the quadricyclane and ester are used, the products (24) compete as dienophile for example, 24d (R = H) added to 20d to give 25.81... 

The hydroesterification of dienes gave both the unsaturated monoesters and saturated diesters.524 In some cases, y-ketoesters were obtained and carbonylation of 1,5-cyclooctadiene in absence of alcohol gave a ketone.525 [PdI2(PBu3)2] was used as catalyst. If the catalyst contained a halide anion, butadiene underwent normal hydroesterification. When halide-free catalysts were used, the reaction took a different course. Dimerization of the diene occurred to give the ester of 3,8-nonadienoic acid as the major product (equation 128).526-528... 

Palladium catalysts that are free of halide ions effect the dimerization and carboxylation of butadiene to yield 3,8-nonadienoate esters. Palladium acetate, solubilized by a tertiary amine or an aromatic amine, gives the best yields and selectivities (equation 57).87 Palladium chloride catalyzes the hydrocarboxylation to yield primarily 3-pentenoates.88 The hydrocarboxylation of isoprene and chloroprene is regio-selective, placing the carboxy function at the least-hindered carbon (82% and 71% selectively) minor amounts of other products are obtained (equation 58). Cyclic dienes such as 1,3-cyclohexadiene and 1,3-cyclooctadiene are similarly hydrocarboxylated. 

We studied the Diels-Alder reaction of levoglucosenone (2) with the very reactive diene 2,3-dimethylene-2,3-dihydrofuran (3),10 the fiiran-based orf/io-quinodimethane, which is readily available by the Flash Vacuum Pyrolysis (FVP) of ester 4.16 Diene 3 dimerizes very rapidly16... 

Over the past ten years, absolute rate data have been reported on the kinetics of several bimolecular silene reactions in solution, including both head-to-tail and head-to-head dimerization the [l,2]-addition reactions of nucleophilic reagents such as water, aliphatic alcohols, alkoxysilanes, carboxylic acids and amines and the ene-addition, [2 + 2]-cycloaddition and/or [4 + 2]-cycloaddition of ketones, aldehydes, esters, alkenes, dienes and oxygen. The normal outcomes of these reactions are summarized in Scheme 1. 

An alternative ester synthesis, the reaction of a carboxylate anion with an alkyl halide, was used by Madejewski [62] for the preparation of ( , )-l,9-dioxacy-clohexadeca-3,1 l-dien-2,10-dione (76) under dilution conditions. This 16-membe-red dilactone represents a precursor for the synthetic norpyrenophorin 77 a, the physiological activity of which corresponds to the one of the natural products pyrenophorin 77b and vermiculin 77c. The lactone 76 can be obtained in 77% yield by dimerization of ( )-7-bromo-2-heptenic acid (75) in DMF in the presence of potassium carbonate. 

Thus acetone, acetaldehyde, and esters condense to dimers in the first stage. From aldehydes we also can obtain six-membered rings such as trioxane from CU2O, paraldehyde from CHaCHO, etc. Dienes often give dimers reversibly. 

Tischchenko-type dimerization of aldehyde is catalyzed by dihydridorutheni-um(II) complexes. In this reaction, aldehyde is initially consumed to reduce Ru(II) to give Ru(0), to which aldehyde oxidatively adds to give a hydrido(acyl)mtheni-um(II) active intermediate affording esters [15]. Hydroacylation of olefins [16] and dienes [17] is also catalyzed by ruthenium complexes (Scheme 14.5). 

Dimer acids. Dimer acids are produced by heating monoene or diene fatty acids (e.g., tall oil acids, a byproduct of wood pulping) with a cationic clay catalyst (92). Typical conditions are 4% montmoriUonite at 230°C for 4—8 hours. After distillation, the product is a complex mixture of acyclic, cyclic, and bicyclic dimers along with some trimer. Dimer acids are dibasic and react with diamines and tria-mines to give polyamides. Imidazole derivatives are used as corrosion inhibitors and esters as lubricants. 

Among the most significant developments in the field of catalysis in recent years have been the discovery and elucidation of various new, and often novel, catalytic reactions of transition metal ions and coordination compounds 13, 34). Examples of such reactions are the hydrogenation of olefins catalyzed by complexes of ruthenium (36), rhodium (61), cobalt (52), platinum (3, 26, 81), and other metals the hydroformylation of olefins catalyzed by complexes of cobalt or rhodium (Oxo process) (6, 46, 62) the dimerization of ethylene (i, 23) and polymerization of dienes (15, 64, 65) catalyzed by complexes of rhodium double-bond migration in olefins catalyzed by complexes of rhodium (24,42), palladium (42), cobalt (67), platinum (3, 5, 26, 81), and other metals (27) the oxidation of olefins to aldehydes, ketones, and vinyl esters, catalyzed by palladium chloride (Wacker process) (47, 48, 49,... 

Elaboration of C-allyl glucose 330 to diene ester 366 by the four steps shown followed by a dihydroxylation-reduction sequence affords a mixture of the lactols 367-370 (represented in acyclic forms) having the D/L-galacto and the D/L-ido configurations in a 5 1 ratio. Hydrogenolysis provides the corresponding C-dimers 371-374, four out of the sixteen possible diastereomers. 

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