Reactions vinylation

Michael reactions Vinyl ) EthynylJ Undergo Michael additions readily q ,/3- Unsaturated ketones... 

The presence of halogen atoms appears to exert little, if any, effect on catalyst activity, but it can influence the course of the metathesis reaction. Vinylic halides are unreactive, as exemplified by the ring-opening polymerization of l-chloro-l,5-cyclooctadiene, which afforded a perfectly alternating copolymer of butadiene and chloroprene (7/2) via polymerization exclusively through the unsubstituted double bond. 

Michael reactions Vinyl Undergo Michael addition 3.2.3.4.5 a,(3-Unsaturated... 

Michael reactions Vinyl, Undergo Michael additions a,P-Unsaturated... 

Isolation of By-product.—During the reaction, vinyl bromide (CH2 CHBr) is formed. It volatilises and is absorbed by the bromine in the wash bottles. The product is washed with dilute caustic soda until excess bromine is removed on fractionating, tribromoethane is obtained (B.P. 187°). 

Keywords Carbopalladation, Asymmetric Heck reaction, Vinylation, Arylation... 

Apart these cases, many other reactions have been investigated, including carbo-nylations, Heck reactions, vinyl substitutions, and hydrosylation. In general, based on available data, it is difficult to establish whether these studies could extend beyond the laboratory scale. However, as Eric Beckman has stressed, when reviewing the use of supercritical or near-critical carbon dioxide in green chemical syntheses [26], the role of these studies in demonstrating the extreme versatility of... 

In this reaction, vinyl chloride, which is formed by the hydrochlorination of acetylene with hydrogen chloride, was not observed from the reaction mixture. This result shows that vinyl chloride does not participate in the formation of dichlorovinylsilane.82... 

The intramolecular reaction can be extended to the cross-annulation reaction of aryl halides with unsaturated compounds [31,33]. For example, 2-halo-biphenyls react with alkynes to give phenanthrene derivatives [96,97]. By using the method, the analogs of hypericin known as antiviral agent (Eq. 45) [98] and indolocarbazoles (Eq. 46) [99] have been prepared. In these reactions, vinyl-palladium intermediates are involved. 

Reactions. Vinyl ethers undergo all of the expected reactions of olefinic compounds plus a number of reactions that are both useful and... 

Skin rash that can be caused by an immune reaction, vinyl chloride... 

First, in a Grignard reaction, vinyl magnesium bromide is added to the dialdehyde 29 to give the corresponding bis-allyl alcohol, which is oxidized in the second step to form the a,P-unsaturated diketone 30 using Dess-Martin periodinane. 

An early example having potential commercial importance comes from tlie Trost laboratory s synthesis of vitamin D analogs (Scheme 6-23) [51], Their combination of vinyl bromide 129 and alkyne 130 to form triene 131 led to a concise and efficient synthesis of (-i-)-alphacalcidiol (134). In this reaction, vinyl bromide 129 participates in a bimolecular Heck reaction with alkyne 130 and the resulting alkenylpalladium intermediate 133 undergoes subsequent intramolecular Heck reaction with the pendant terminal alkene to provide 131. Under the reaction conditions, some of the desired product undergoes a [1,7]-hydrogen shift to yield 132. After thermal recycling of the minor component, a remarkable 76% yield of 131 was obtained. 

As outlined in Chap. 20, condensation polymerization can involve the reaction of any two species present in a condensation polymerization system. The result is a generally slow progression toward moderate molecular weights if conditions are chosen to help drive the reaction to very near completion. These requirements and the results are listed for convenience of comparison with chain reaction (vinyl-type) polymerization discussed in detail here (Table 22.3). 

Characteristic Condensation (step-reaction) polymerization Chain reaction (vinyl-type) polymerization... 

Other reports include reactions in supercritical ethylene, promotion by molecular sieves, and the effect of a phosphine sulfide. Clusters such as methylidynetricobalt nonacarbonyl are also effective catalyst of the Pauson-Khand reaction." Vinyl esters are identified as surrogates for ethylene. ... 

Methyl halides and primary alkyl halides undergo only Sn2 reactions, tertiary alkyl halides undergo only SnI reactions, vinylic and aryl halides undergo neither Sn2 nor SnI reactions, and secondary alkyl halides and benzylic and al-lylic halides (unless they are tertiary) undergo both SnI and Sn2 reactions. When the stmcture of the alkyl halide allows it to undergo both Sn2 and SnI reactions, the Sn2 reaction is favored by a high concentration of a good nucleophile in an aprotic polar solvent, while the SnI reaction is favored by a poor nucleophile in a protic polar solvent. 

Wittig reactions. Vinylic chalcogenides are formed under sonochemical conditions using K2CO3 as base. 

Primary, secondary and tertiary alkyl chlorides, bromides or iodides all undergo reaction (vinyl halides and alkyl fluorides do not), as do cycloalkyP" " and benzyP " halides. Apart from the compilation of examples by Kinnear and Perren ", other examples are spread very widely and rather thinly throughout the literature. Some isomerization is to be found when using certain alkyl halides for example, -propyl and -butyl halides afford the isopropyl- and (l-methylpropyl)-phosphonic dichlorides, and isobutyl chloride yields r r/-butylphosphonic dichloride ". Whilst Me3SiCH2Cl affords the expected phosphonic dichloride, neopentyl chloride yields (l,l-dimethylpropyl)phosphonic dichloride ". 1,5-Dichloropentane reacts but affords only (4-chloro-l-methylbutyl)phosphonic dichloride " ... 

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