Reactions with Olefins

Its reactions with olefins, governed by steric rather than electronic factors, are very sluggish. Even simple 1-alkenes require 8 h at 25°C for complete reaction. In contrast, alkynes are hydroborated with great ease to alkenylboranes, high steric requirements of the reagent preventing dihydroboration (117). 

Chlorine can be removed by either activated carbon adsorption or by reaction with olefins such as ethylene over-activated carbon at temperatures of 30—200°C (44). Addition of Hquid high boiling paraffins can reduce the chlorine content in the HCl gas to less than 0.01% (45). 

Chlorine heptoxide is more stable than either chlorine monoxide or chlorine dioxide however, the CX C) detonates when heated or subjected to shock. It melts at —91.5°C, bods at 80°C, has a molecular weight of 182.914, a heat of vapori2ation of 34.7 kj/mol (8.29 kcal/mol), and, at 0°C, a vapor pressure of 3.2 kPa (23.7 mm Hg) and a density of 1.86 g/mL (14,15). The infrared spectmm is consistent with the stmcture O CIOCIO (16). Cl O decomposes to chlorine and oxygen at low (0.2—10.7 kPa (1.5—80 mm Hg)) pressures and in a temperature range of 100—120°C (17). It is soluble in ben2ene, slowly attacking the solvent with water to form perchloric acid it also reacts with iodine to form iodine pentoxide and explodes on contact with a flame or by percussion. Reaction with olefins yields the impact-sensitive alkyl perchlorates (18). 

G-All lation. Siace para-alkylated derivatives of DPA are widely used ia large volumes as antioxidants (qv), the most important reaction of DPA is the acid catalyzed reaction with olefins (2,3). Alkylation is carried out by adding the olefin to a mixture of DPA and an acid catalyst, such as AIQ. ... 

These singlet and triplet state species exhibit the important differences in chemical behavior to be expected. The former species, with their analogy to carbonium ions, are powerful electrophiles and the relative rates of their reaction with a series of substrates increases with the availability of electrons at the reaction center their addition reactions with olefins are stereospecific. Triplet state species are expected to show the characteristics of radicals i.e., the relative rates of additions to olefins do not follow the same pattern as those of electrophilic species and the additions are not stereospecific. 

The preparation of cyclopropane derivatives has been greatly facilitated by the development of carbene-type intermediates (see Chapter 13) and their ready reaction with olefins. The preparation of phenylcyclopropane from styrene and the methylene iodide-zinc reagent proceeds in only modest yield, however, and the classical preparation of cyclopropane derivatives by the decomposition of pyrazolines (first employed by Buchner in 1890) is therefore presented in the procedure as a convenient alternative. 

Phenyltnhalomethylmercunals, reaction with olefins to form dichloro-cyclopropanes, 46,100 Phenylurea, 46, 72 Phosgene, 46, 98... 

However, consideration of polar factors in the traditional sense does not provide a ready explanation for the regiospecificity shown by the r butoxy radicals (which arc electrophilic, Tabic 1.3) in their reactions with the tluoro-olcfins (Tabic 1.2).22,23 Apparent ambiphilicity has been reported21 for other not very electrophilic radicals in their reactions with olefins and has been attributed to the polarizability of die radical. 

In contrast to alkoxycarbene complexes, most aminocarbene complexes appear too electron-rich to undergo photodriven reaction with olefins. By replacing aliphatic amino groups with the substantially less basic aryl amino groups, modest yields of cyclobutanones were achieved (Table 10) [63], (Table 11) [64]. Both reacted with dihydropyran to give modest yields of cyclobutanone. Thio-carbene complexes appeared to enjoy reactivity similar to that of alkoxycar-benes (Eq. 15) [59]. 

One of the earliest reported thermal reactions of Fischer carbene complexes was the reaction with olefins to give cyclopropanes [127]. More recently it has been shown that photolysis accelerates inter molecular cydopropanation of electron-poor alkenes [128]. Photolysis of Group 6 imine carbenes with alkenes... 

Reaction of Unsaturated Compounds with Dialkyl Phosphites The diesters of phosphorous acid are somewhat resistant to oxidation and used as intermediates for the reaction with olefins forming phosphonic acids. The reaction takes place in the presence of free radical initiators, such as di-/-bu-tyl peroxide [104,105]. 

Few CIDNP studies on free radical reactions with olefins and related unsaturated molecules have been reported, and relatively little chemically useful information seems to have been derived, despite the potential relevance in polymerizing systems. Thus CIDNP has been reported in the decomposition of benzoyl peroxide in the presence of styrene and... 

What we have shown here is the fact that large inverse values can be obtained for the Br2 addition to a "normal" olefin which should pass through a symmetrical, or nearly so, transition state. Of course, more work involving other systems would be beneficial in assessing the scope and limitation of the use of the a-deuterium kie s in mechanistic studies of Br2 and Br3 reactions with olefins. 

I. Joffee, in "The Production of Bromine Chloride and Its Reactions with Olefins", DSB-BCL First Intermediate Report, March 31, (1974). 

Although the cracking of mbbers is related to the reaction of ozone on the double bond, it must be mentioned that ozone reacts also with sulfur cross-links. These reactions, however, are much slower. The reaction of ozone with di- and polysulfides is at least 50 times slower than the corresponding reaction with olefins [49]. 

Although nitrile oxide cycloadditions have been extensively investigated, cycloadditions of silyl nitronates, synthetic equivalent of nitrile oxides in their reactions with olefins, have not received similar attention. Since we found that the initial cycloadducts, hl-silyloxyisoxazolidines, are formed with high degree of stereoselectivity and can be easily transformed into isoxazolines upon treatment with acid or TBAF, intramolecular silylnitronate-olefin cycloadditions (ISOC) have emerged as a superior alternative to their corresponding INOC reactions [43]. Furthermore, adaptability of ISOC reactions to one-pot tandem sequences involving 1,4-addition and ISOC as the key steps has recently been demonstrated [44]. 

D. L. Phillips, W.H. Fang, and X. Zheng, Isodiiodomethane is the methylene transfer agent in cyclopropanation reactions with olefins using ultraviolet photolysis of diiodomethane in solutions a density functional theory investigation of the reactions of isodiiodomethane, iodomethyl radical, and iodomethyl cation with ethylene. J. Am. Chem. Soc. 123(18), 4197-4203 (2001). 

Reactions of the hydrido(hydroxo) complex 2 with several substrates were examined (Scheme 6-14) [6]. The reactions are fairly complicated and several different types of reachons are observed depending on the substrate. Methyl acrylate and small Lewis bases such as CO, P(OMe)3, BuNC coordinate to the five-coordinated complex 2 affording the corresponding six-coordinate complexes. In reactions with the unsaturated bonds in dimethylacetylenedicarboxylate, carbon dioxide, phenylisocyanate indications for the addition across the O-H bond but not across the Os-OH bond were obtained. In reactions with olefins such as methyl vinyl ketone or allyl alcohol, elimination of a water molecule was observed to afford a hydrido metalla-cyclic compound or a hydrido (ethyl) complex. No OH insertion product was obtained. 

A few further general examples of zinc catalytic activity or reactivity include the following. Other zinc-containing systems include a zinc phenoxide/nickel(0) catalytic system that can be used to carry out the chemo- and regioselective cyclotrimerization of monoynes.934 Zinc homoenolates have been used as novel nucleophiles in acylation and addition reactions and shown to have general utility.935,936 Iron/zinc species have been used in the oxidation of hydrocarbons, and the selectivity and conditions examined.362 There are implications for the mechanism of metal-catalyzed iodosylbenzene reactions with olefins from the observation that zinc triflate and a dizinc complex catalyze these reactions.937... 

Acyclic S-S dications 51 and 52 also give 1,2-disulfonium salts 90 in reactions with olefins.79 Formation of a mixture of diastereomers is observed in the case of 1,2-disubstituted alkenes. Reaction with conjugated dienes leads exclusively to the product of 1,4-addition 89 as mixtures of E- and Z-products whose ratio depends on steric factors (Scheme 34).79... 

On a first, very broad, approximation singlet oxygen behaves somehow like ethylene. Three types of reactions of 102 are usually observed and have been utilized in organic synthesis 606 608) a) the Diels-Alder like cycloaddition to dienes (6.1) b) the ene reaction with olefins (6.2) and c) cycloaddition to activated double bonds (6.3). 

In marked contrast to the results of Gassman and Schrock, major differences were noted by Casey and co-workers in a series of studies utilizing phenylcarbene-substituted W(0) complexes in reactions with olefins. The H NMR spectra of new phenylcarbene tungsten and iron (69) complexes indicate a substantial positive charge residing on the carbene carbon, and as expected, these complexes readily form ylides on reaction with phosphines ... 

These reactions of diclorine with olefins are endothermic, AH varies from 63 kJ mol-1 (Ph2C=CH2) to 191 kJ mol-1 (MeC=CMe). The rate constants of chlorine reactions with olefins calculated by the IPM method are presented in Table 3.16. 

Triazoline-3,5-dione 184 underwent an ene reaction with olefins 183 to yield trialkylated allylic urazoles 185, which were further elaborated into allylic amines 186 . DBU has been found to be a mild and convenient base for the alkylation of 1,2,4-triazole with various alkyl halides in the high yielding syntheses of 1-substituted-1,2,4-triazoles <00TL1297>. 

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