Dienes vinylation

Some remarks concerning the scope of the cobalt chelate catalysts 207 seem appropriate. Terminal double bonds in conjugation with vinyl, aryl and alkoxy-carbonyl groups are cyclopropanated selectively. No such reaction occurs with alkyl-substituted and cyclic olefins, cyclic and sterically hindered acyclic 1,3-dienes, vinyl ethers, allenes and phenylacetylene95). The cyclopropanation of electron-poor alkenes such as acrylonitrile and ethyl acrylate (optical yield in the presence of 207a r 33%) with ethyl diazoacetate deserve notice, as these components usually... 

Reactions of germylenes with 1,3-dienes, vinyl ketones, ot-diketones, vinyl imines, and a-diimines gave corresponding [4 - - 1] cycloadducts (Scheme 14.55). ... 

Though thioacetone polymerizes spontaneously, by free-radical initiation, and by base initiation, it does not form copolymers in any of these systems. Efforts to obtain copolymers with dienes, vinyl compounds, acrylates, aldehydes, and epoxides have failed. 

Stereochemistry is largely lost in die diene vinylation, at least at 100 C, as evidenced by die reaction of (Z,E)-3-methyl-2,4-pentadienoic acid shown in equation (40). 

We have not commented on the criteria determining the actual polymerisability of a monomer by cationic initiation, since they are well known The present review deals with monomers belonging to the n-donor (olefins, dienes, vinyl aromatics) and n-and n-donor (vinyl ethers, vinyl amines, vinyl sulphides) families, but not with purely n-donor and 6-donor monomers. 

Coupling of vinyl bromides 1, h-dienes Vinyl bromides can undergo inter-or intramolecular coupling to 1,3-dienes in the presence of Pd(OAc)2, a triaryl-phosphine (1.25 equiv.), and a large excess of K2CO3 (7.5 equiv.). 

The procedure can be employed with alkenes, allenes, conjugated dienes, vinylic cyclopropanes, and isocyanides, and the corresponding thioselenation products are obtained regioselectively in good yields, as exemplified by the compounds in Scheme 15.68 [148]. 

Carbo and heteroannulation of 1,2-, 1,3-, 1,4-dienes, vinyl cyclopropanes, vinyl cyclobutanes catalyzed by arylmercury, thallium or palladium. 

Cobalt is another metal which has been successfully used in asymmetric cyclopropanation. A chirally modified catalytic system for selective cyclopropanation of phenyl-, vinyl- or alkoxy-carbonyl-conjugated terminal double bonds with diazoacetates is formed from cobalt(ll) chloride and (+)-a-camphorquinonc dioxime27,69 71 and similar systems 09. Best optical yields are achieved with styrene and the bulky 2,2-dimethylpropvl diazoacetate which gives 2,2-dimethylpropyl /ra .v-2-phenyl-l-cyclopropanecarboxylate in 88% ee and the as-isomer in 81%ee7n. No cyclopropanation occurs with alkyl-substituted or cyclic alkenes, cyclic or sterically hindered acyclic 1.3-dienes, vinyl ethers and phenylethyne. 

Diene Vinyl Ether Catalyst Ratio (endojexo) d.r.b (Major Adduct) Yield <%)... 

EPDM formulations are increasingly popular for medium-voltage, up to 105°C continuous-use temperature, wire and cable covering. EPDMs are good vulcan-izates, providing improved wet electrical properties. When diene vinyl norbornene is incorporated on the EPDM backbone by a gel-free process, a significantly improved EPDM terpolymer is obtained for wire and cable applications. 

Diene Vinyl-9-BBN Vinyldimethyl- borane Vinyl-DMB Trivinylborane... 

Radical oxidative cycloaddition of 4-hydroxycoumarins to alkenes has also emerged as a powerful tool for the rapid construction of dihydrofuro[3,2-c] coumarins [83-87]. The fact that 4-hydroxycoumarins behave as 1,3-dicarbonyI systems allows the easy generation of a,a-dicarbonyl radicals, which can be readily added to the C=C bond of the alkene. First examples of this reaction were described in 1998 by Lee and coworkers employing Ag2C03/celite (Fetizon reagent) as promoter [83]. A variety of olefins such as styrenes, dienes, vinyl ethers. 

Ethylene Styrene Vinyl halides Dienes Vinyl ethers Dialkyl olefins... 

Multiple efficient catalysts were reported for the intramolecular process, while the intermolecular process has been studied predominantly for alkynes. The reactivity of the unsaturated fragment decreases in the order alkyne > allene diene > vinyl arene unactivated alkene with the intermolecular hydroamination of simple alkenes representing the most difficult transformation. The hydroamination of all types of carbon-carbon unsaturated fragments will be covered in this chapter. 

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