Oxygen ions with alkenes

Reaction of hydrogen sulphite ions with alkenes, in the presence of either oxygen or peroxides170-177, produces a reasonable yield of the sulphonic acid salt (equation 24), formed by anti-Markovnikov addition. Alkynes also undergo a similar reaction178, except in this case a disulphonate salt is formed (equation 25). 

Early mechanistic studies have indicated that the oxypalladation step in the Wacker process proceeds through an <37z/z-pathway,399 although recent deuterium-labeling experiments have shown the viability of a yy/z-mechanism involving insertion of a metal-coordinated oxygen into the alkene.400,401 For example, with excess chloride ion present, the Wacker-type cyclization of a deuterated phenol system occurred in a primarily //-pathway, whereas the oxypalladation step favored a yy/z-mode in the absence of excess chloride ion (Scheme 16). Thus, either mechanism may be operative under a given set of experimental conditions. 

The Mo+ ion was generally less reactive to alkenes than the other ions. Additions of the alkene to the Mo+ and [MoO]+ with loss of H2 or 2H2 were the major reaction products similar to the alkanes. The reactions of [Mo02]+ with alkenes gave a variety of products, the major reactions being reduction by loss of an oxygen atom. 

The paramagnetic oxygen ions 0 , 01> and 0J have been formed on magnesium oxide and studied by EPR spectroscopy. The reactivity of these ions with hydrocarbons follows the sequence 0 >>03> >02. Both with alkanes and alkenes the initial reaction is thought to be hydrogen atom abstraction. 

Alkanes—Continued reactions—Continued with ozonide ions, 135 with superoxide ions, 134-35 role of oxygen ions in oxidation. 138-41 Alkenes, reactions with oxygen ions, 134 with ozonide ions, 135 with superoxide ions, 134-35 Aluminosilicate gels, alkali cations, 241... 

Other alkyl hypohalites usually add to carbon-carbon multiple bonds in a free-radical process.155-158 Ionic additions may be promoted by oxygen, BF3, or B(OMe)3.156-160 While the BF3-catalyzed reaction of alkyl hypochlorites and hypo-bromites gives mainly halofluorides,159 haloethers are formed in good yields but nonstereoselectively under other ionic conditions.156-158 160 In contrast, tert-BuOI reacts with alkenes in the presence of a catalytic amount of BF3 to produce 2-iodoethers.161 Since the addition is stereoselective, this suggests the participation of a symmetric iodonium ion intermediate without the involvement of carbocationic intermediates. 

Ethers are compounds that have two organic groups bonded to the same oxygen atom, ROR. The organic groups can be alkyl, vinylic, or aryl, and the oxygen atom can be in a ring or in an open chain. Ethers are prepared by either the Williamson ether synthesis, which involves Sf t2 reaction of an alkoxide ion with a primary alkyl halide, or the alkoxymercuration reaction, which involves Markovnikov addition of an alcohol to an alkene. 

Two reviews address the reactions of bare transition metal atoms and ions with hydrocarbons in the gas phase and the reactions of monosubstituted alkanes with bare transition metal ions. 2 A study of the reactivity of ground-state, neutral transition metal atoms from the left hand side of the 4d series (Y through Mo) shows that they are unreactive towards linear alkanes but that they will react with cyclopropane and alkenes.3 Atomic metal cations form a 1 1 adduct with tribenzocyclotriyne in a Fourier-transform ion cyclotron resonance spectrometer. Reaction of molecular oxygen with M(C2H4) results in ligand exchange to M02 for the early first row transition metals. Activation of the O—O bond and product formation is observed for ccnnplexes of Sc+,Ti+andV+.5... 

In the reactions using NO as a reagent, there is always a problem that the true active species is unidentified. This is due to the possibility that a trace amount of oxygen or a metal ion can function as a catalyst for the reaction of NO. Pure NO does not react with alkenes, for example, isobutene or similar alkyl-substituted olefins [22]. The main isolated products were found to be nitroalkenes, and it was postulated that the small amounts of NO formed from the oxidation of NO ... 

Another category is that of radical and radical ion chain processes that may be involved in reactions of mechanistic and applicative interest. The oxygenation of tetrasubstituted alkenes and three-membered (hetero)cycles occurs in many cases via photoinduced electron transfer generating a radical cation (Scheme 7.9a). A chain process may take place in every case where the product is more easily oxidized than the reagent. Indeed, this principle has been q)pUed in polymers and (juantum amplified isomerization via a radical cation chain. These processes has been found to (xxur with moderate efficiency in the presence of electron-poor molecules, such as dicyanoan-thracene and A-methylcjuinolinium hexafluorophosphate, both when the donor had... 

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