Alkene cleavage involvement, reactions

The reaction type (a) in Scheme 1 for the allylic amination reaction uses substrates which have an allylic C-X (X = heteroatom, halide) bond and is mainly nucleophilic amination of functionalized alkenes, whereas reaction type (b) is a direct allylic amination of an alkene, based on electrophilic amination of nonfunctionalized alkenes and involves a cleavage of a C-H bond. 

The dimerization of methylenecyclopropane to 5-methylenespiro[2.4]heptane 2 was usually observed during the palladium(0)-catalyzed reaction of methylenecyclopropane with alkenes which involved the cleavage of the three-membered ring giving 6. °... 

Overall the reaction leads to addition of two hydroxyl groups to the double bond and IS referred to as hydroxylation Both oxygens of the diol come from osmium tetraox ide via the cyclic osmate ester The reaction of OSO4 with the alkene is a syn addition and the conversion of the cyclic osmate to the diol involves cleavage of the bonds between oxygen and osmium Thus both hydroxyl groups of the diol become attached to the same face of the double bond syn hydroxylation of the alkene is observed... 

Heterogeneous reaction (Section 6 1) A reaction involving two or more substances present in different phases Hydro genation of alkenes is a heterogeneous reaction that takes place on the surface of an insoluble metal catalyst Heterolytic cleavage (Section 4 16) Dissociation of a two electron covalent bond in such a way that both electrons are retained by one of the initially bonded atoms Hexose (Section 25 4) A carbohydrate with six carbon atoms High density lipoprotein (HDL) (Section 26 11) A protein that carries cholesterol from the tissues to the liver where it is metabolized HDL is often called good cholesterol Histones (Section 28 9) Proteins that are associated with DNA in nucleosomes... 

There are two plausible reactions which lead to the observed products of the metathesis of alkenes. The first possibility involves cleavage of a carbon-carbon single bond adjacent to the double bond the second involves cleavage of the double bond itself. The following transalkylation... 

Thermal cleavage of cyclobutanesto give two alkene molecules (cyclorever-sion, the reverse of 2 -I- 2 cycloaddition) operates by the diradical mechanism, and the [ 2s -I- o2a] pathway has not been found " (the subscripts a indicate that cr bonds are involved in this reaction). 

Nickel-bpy and nickel-pyridine catalytic systems have been applied to numerous electroreductive reactions,202 such as synthesis of ketones by heterocoupling of acyl and benzyl halides,210,213 addition of aryl bromides to activated alkenes,212,214 synthesis of conjugated dienes, unsaturated esters, ketones, and nitriles by homo- and cross-coupling involving alkenyl halides,215 reductive polymerization of aromatic and heteroaromatic dibromides,216-221 or cleavage of the C-0 bond in allyl ethers.222... 

By far the most commonly used - though not the most environmentally friendly -solvent is CCl (or more usually water-CCl ). In a classic paper Sharpless et al. showed that oxidation reactions of RuO (and other some Ru-based oxidants) were accelerated by addition of a little acetonitrile to the conventional water-CCl biphasic mixture. It was suggested that the CH3CN might function as a mild donor stabilising a lower oxidation state carboxylato Ru species which could be involved in the catalytic process [260]. A comparative study of CCl, acetone, ethyl acetate, cyclohexane and acetone for cleavage of alkenes and alkynes by RuClg/aq. IO(OH)3/solvent showed that cyclohexane was the most effective [216]. Other solvents sometimes... 

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