Functionalization of Olefins

Wacker cyclization has proved to be one of the most versatile methods for functionalization of olefins.58,59 However, asymmetric oxidative reaction with palladium(II) species has received only scant attention. Using chiral ligand 1,1 -binaphthyl-2,2 -bis(oxazoline)-coordinated Pd(II) as the catalyst, high enantioselectivity (up to 97% ee) has been attained in the Wacker-type cyclization of o-alkylphenols (66a-f) (Scheme 8-24). 

FIGURE 3-6 Mass concentration of aerosol formation from olefin-ozone reaction as a function of olefin concentration, r, residence time in the flow reactor. Reprinted with permission from Burton et ai. 

The observation that the previously described diacetoxylation of olefins by means of tel-lurinic anhydrides produces quantitative yields of the corresponding ditellurides suggested the oxidative functionalization of olefins employing diphenyl diteUuride combined with an oxidizing agent instead of the tellurinic anhydride. ... 

Heteroatoni groups such as boron or silicon can activate or direct synthetic reactions. Use of such activation has become of major importance in organic syntheses. Examples in this volume are BORANES IN FUNCTIONALIZATION OF DIENES TO CYCLIC KETONES BICYCLO[3.3.1]NONAN-9-ONE and BORANES IN FUNCTIONALIZATION OF OLEFINS TO AMINES 3-PINANAMINE. Use of trimethylsilyl or trimethyl-silyloxy groups to activate a 2-butenone or a butadiene are illustrated by the preparations 3-TRIMETHYLSILYL-3-BUTEN-... 

Benzene alkylation over Y zeolites has been studied as a function of olefin, olefin aromatic ratio, temperature, and zeolite cation form. The rate has been modeled, and the rate-limiting process has been quantified as product desorption. 

Cundall has done extensive work on benzene231,237 and acetone243 sensitized isomerizations of the 2-butenes, and in every case reported a photostationary or radiostationary trans/cis ratio of 1.27-1.37. Sato, however, has measured a value of unity for the benzene photosensitized isomerization.510 With higher homologs, from 2-pentene to 2-octene, benzene-sensitized isomerizations yield trans/cis ratios of 1.0,238 while acetone-sensitized isomerization of the 2-pentenes in solution yields a ratio of 1.65.244 At present no explanation is possible for the differences between 2-butene and 2-pentene. Until much more information is gathered relating to rates of triplet energy transfer as functions of olefin structure, sensitizer, and medium, the natural decay ratios of each olefin s common triplet cannot be deduced from photostationary trans/cis ratios. 

The di-f-butylhydroxylamine and di-/-butylhydroxylamine ethers probably result from DTBN scavenging of radicals produced by hydrogen atom abstraction from the olefins by excited 3-ethoxyisoindolenone (50). The observed destruction of DTBN as a function of olefin structure is consistent with this mechanism. Based upon allyl radical stability and the statistical factor, excited 3-ethoxyisoindolenone should abstract hydrogen atoms more rapidly from tetraroethylethylene than from ds-2-butene. 

The reaction conditions used were quite mild, e.g. 1 atm O2 ambient temperature. Reaction rate was studied both as a function of olefin chain length and as a function of solvent composition. It was found that In a mlcroemulslon the rate of reaction decreased with Increasing chain length. Catalyst turnover rates, after two hours, were Cj q=19.1, C, =15.7 and Ci8 12.4. 

The solvomercuration of alkenes has an important synthetic valne since it allows the asymmetric functionalization of olefins. Although a large number of organomercurials have been isolated from these reactions, more commonly, they are reduced with alkaline NaBELi to yield the corresponding metal-free organic species (see Section 4.1). In this way, olefins can be converted into a wide range of organic species such as alcohols, ethers, and amines. 

Figure 12.4. Instantaneous isothermal heat release Q as function of olefin conversion for hydroformylation of long-chain olefins with cobalt phosphino-hydrocarbonyl catalysts (schematic).

Vicinal functionalization of olefins or acetylenes is an efficient manipulation of these functional groups, as they have two consecutive reactive centers. From this standpoint, carbometallation of olefins and acetylenes is an attractive transformation, owing to the concomitant formation of a new carbon-carbon bond at one terminus and a Grignard reagent at another position, the latter of which permits an introduction of a variety of carbon or heteroatom electrophiles [Eq. (10)]. 

Palladium-Catalyzed Allylic C-H Bond Functionalization of Olefins... 

The reaction of simple olefins with S03 and S03 complexes and derivatives has been demonstrated to yield allylic and vinylic sulfonic acids, hydroxysulfonic acids, and other neutral products (10). The product distribution is a function of olefin type, sulfonation reagent, solvent, and reaction conditions. 

Functionalization of Olefinic Polymer and Copolymer Blends in the Melt... 

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