Alkene reductive arylations

Other limitations of the reaction are related to the regioselectivity of the aryl radical addition to double bond, which is mainly determined by steric and radical delocalization effects. Thus, methyl vinyl ketone gives the best results, and lower yields are observed when bulky substituents are present in the e-position of the alkene. However, the method represents complete positional selectivity because only the g-adduct radicals give reductive arylation products whereas the a-adduct radicals add to diazonium salts, because of the different nucleophilic character of the alkyl radical adduct. ... 

This section contains dehydrogenations to form alkenes and unsaturated ketones, esters and amides. It also includes the conversion of aromatic rings to alkenes. Reduction of aryls to dienes is found in Section 377 (Alkene-Alkene). Hydrogenation of aryls to alkanes and dehydrogenations to form aryls are included in Section 74 (Alkyls from Alkenes). 

Reductive arylation of enones, TiCl3 induces homolytic dediazotization of diazonium salts to produce aryl radicals, which arylate electron-deficient alkenes.1 Example ... 

The rate-determining step in the ionic hydrogenation reaction of carbon-carbon double bonds involves protonation of the C==C to form a carbocation intermediate, followed by the rapid abstraction of hydride from the hydride source (equation 45). ° There is a very sensitive balance between several factors in order for this reaction to be successful. The proton source must be sufficiently acidic to protonate the C—C to form the intermediate carbocation, yet not so acidic or electrophilic as to react with the hydride source to produce hydrogen. In addition, the carbocation must be sufficiently electrophilic to abstract the hydride from the hydride source, yet not react with any other nucleophile source present, i.e. the conjugate anion of the proton source. This balance is accomplished by the use of trifluoroacetic acid as the proton source, and an alkylsilane as the hydride source. The alkene must be capable of undergoing protonation by trifluoroacetic acid, which effectively limits the reaction to those alkenes capable of forming a tertiary or aryl-substituted carbocation. This essentially limits the application of this reaction to the reduction of tri- and tetra-substituted alkenes, and aryl-substituted alkenes. 

Reduction of Vinyl Halides to Alkenes and Aryl Halides to Arenes... 

Palladium-catalyzed reductive arylations of alkenes have also been applied to intramolecular additions70 75 77. 

A new Pd(0) -catalyzed carboiodination reaction of alkenes with aryl iodides, which generates a C-C and a C-I bond, involves a rate-determining reductive elimination step to form the C(sp ) - I bond, which is facilitated by bulky monophosphine ligands by preventing the formation of tetracoordinated intermediates [365]. 

The highly selective sy/j-double arylation or alkenylation reaction of alkynes or alkenes with aryl or alkenylstannane reagents was realized via a possible oxidative addition, insertion, transmetalation, and reductive elimination mechanism (eqs 31 and 32). ... 

A. Hydrogenation of Alkenes (and Aryls) B. Formation of Aryls C. Alkylations and Arylations of Alkenes D. Conjugate Reduction of Conjugated Carbonyl Compounds and Niuiles E. Conjugate Alkylations F. Cyclopropanations, including balocyclopropaiiations... 

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