Performic acid alkenes

The side chain alkylation of alkyl benzenes is usually performed with alkenes as alkylating agents in the presence of strong-acid catalysts (256,257). The use of highly basic catalysts such as alkali metals, their hydrides, and sodium and potassium complexes for alkylation of alkylaromatic hydrocarbons has also been reported (256,257). The reaction mechanism proposed by Pines et al. (258) involves the addition of a benzylic carboanion to the alkene (Scheme 41). 

Performic acid is an unstable, hazardous percarboxylic acid, and must always be generated in situ. Epoxidation with in situ performic and peracetic acid are well established commercial processes. They find application in the epoxidation of alkenes, particularly those of high molecular weight. Many such epoxides are produced on a large scale, and can be classified as vegetable oils, unsaturated esters, unsaturated acids, a-alkenes, natural polymers and synthetic polymers. The most important vegetable oil which is epoxidized commercially is soyabean oil. World production of epoxidized soyabean oil (ESBO) exceeds 150000 metric tons per annum. Epoxidized linseed oil is also important, but produced at a lower rate than ESBO. Both products are formed by usual in situ performic and peracetic acid techniques.23,24 Typical procedures are outlined in Table 3.1.25... 

Pentane-1,2-diol is an important intermediate for the production of fungicides125 and can be continuously prepared by reacting pent-l-ene with a solution of perpropionic acid in benzene, and subsequent hydrolysis of the epoxide.126 The diol yield of 92% from the alkene is much higher than with performic acid (Figure 3.26).116... 

Formaldehyde, benzaldehyde and aniline react violently with 90% performic acid (Ref 1). An unspecified organic compd was added to the acid, and soon after the initial vigorous reaction had subsided, the mixt expld violently (Ref 3). Reaction with alkenes is vigorously exothermic, and adequate cooling is necessary. Reactions with performic acid can be more safely accomplished by the slow addition of hydrogen peroxide to a soln of the compd in formic acid (Ref 4)... 

The relevant literature in this subfield is too voluminous to be detailed here. Overviews are available [62], and only a few recent references to the newest publications are given below. Oxidations of the following types have been performed alcohol - ketone [63] aldehyde —> acid alkene —> diol or epoxide [64-67] al-kene - aldehyde, acid 1-alkyne —> ketoaldehyde and acid (1 C-atom shorter) internal alkyne —> a,/3-epoxyketone vic-diol —> 1,2-diketone [68] or hydroxyketone [69] amine —> amine oxide [70] aromatic amine —> nitrosobenzene, nitrobenzene, azoxybenzene [71]. 

The following modifications of substituents without alteration of the pyrido[3,4-r]pyridazine system have been performed oxidation alkenes to carboxylic acids (ArCH=CHPh - ArC02H) 104 condensation methyl groups with carbaldehydes (ArMe- ArCH = CHPh) Ar = pyridolT -elpyridazinyl.104... 

For example, the NPA charges for the DMDO and performic oxidations of ethene have been compared. " The ratio of the electrophilic interaction involving electron density transfer from the alkene to the 0-0 ct orbitals can be compared with the nucleophilic component involving back donation from the oxidant to the alkene t orbital. By this comparison, performic acid is somewhat more electrophilic. 

Lately the Berke group has reported that enforced NO bending can boost the performance of alkene hydrogenations via co-catalysis of Re(I) diiodo rntMumitrosyl complexes and attached silylium Lewis acids [31] (Scheme 50). CombinatiOTis of the... 

Alkenes are good nucleophiles by virtue of their ji electron density. Performic acid is electrophilic at the terminal hydroxyl group, as a result of the weak 0-0 bond and the good leaving group. 

Alkenes are readily epoxidised by electrophilic oxygen sources such as performic acid. 

So, we must find another route. Instead of performing acid-catalyzed hydration first, we could first reduce the alkyne (in the presence of a poisoned catalyst), giving an alkene. This alkene can then be treated with dilute aqueous acid to give Markovnikov addition of H and OH, resulting in the desired product ... 

Alkenes. The sulfation of low molecular weight alkenes using concentrated sulfuric acid is amenable to continuous operation. Good agitation is required and the reaction is performed at 70—80°C. Dialkyl sulfates ate also formed. Longer (C 2 i8) carbon chain alkenes yield detergent products. Order... 

Chlorohydnns and 1,2-dichloro denvatives are obtamed by oxidation of alkenes with fert-butyl hypochlorite when the reaction is performed in acetic acid instead of water, chlorohydrm acetate is formed [Ji] (equation 25)... 

In 1970, it was disclosed that it is possible to achieve the conversion of dimethylformamide cyclic acetals, prepared in one step from vicinal diols, into alkenes through thermolysis in the presence of acetic anhydride." In the context of 31, this two-step process performs admirably and furnishes the desired trans alkene 33 in an overall yield of 40 % from 29. In the event, when diol 31 is heated in the presence of V, V-dimethylforrnamide dimethyl acetal, cyclic dimethylformamide acetal 32 forms. When this substance is heated further in the presence of acetic anhydride, an elimination reaction takes place to give trans olefin 33. Although the mechanism for the elimination step was not established, it was demonstrated in the original report that acetic acid, yV, V-dimethylacetamide, and carbon dioxide are produced in addition to the alkene product."... 

To mimic the square-pyramidal coordination of iron bleomycin, a series of iron (Il)complexes with pyridine-containing macrocycles 4 was synthesized and used for the epoxidation of alkenes with H2O2 (Scheme 4) [35]. These macrocycles bear an aminopropyl pendant arm and in presence of poorly coordinating acids like triflic acid a reversible dissociation of the arm is possible and the catalytic active species is formed. These complexes perform well in alkene epoxidations (66-89% yield with 90-98% selectivity in 5 min at room temperature). Furthermore, recyclable terpyridines 5 lead to highly active Fe -complexes, which show good to excellent results (up to 96% yield) for the epoxidation with oxone at room temperature (Scheme 4) [36]. 

The hydroamination of alkenes has been performed in the presence of heterogeneous acidic catalysts such as zeolites, amorphous aluminosilicates, phosphates, mesoporous oxides, pillared interlayered clays (PILCs), amorphous oxides, acid-treated sheet silicates or NafioN-H resins. They can be used either under batch conditions or in continuous operation at high temperature (above 200°C) under high pressure (above 100 bar). 

With the renaissance in alkene chemistry engendered by the rising versatility of olefin metathesis in both fine chemical and commodity production, new methods for alkene isomerization are of increasing interest and importance. Alkene isomerization can be performed using Bronsted-Lowry acid or base catalysis (1). However, these reactions are limited to substrates which tolerate carbanionic or carbocation intermediates, and are susceptible to undesired side reactions. 

The hydrogenation of simple alkenes using cationic rhodium precatalysts has been studied by Osborn and Schrock [46-48]. Although kinetic analyses were not performed, their collective studies suggest that both monohydride- and dihydride-based catalytic cycles operate, and may be partitioned by virtue of an acid-base reaction involving deprotonation of a cationic rhodium(III) dihydride to furnish a neutral rhodium(I) monohydride (Eq. 1). This aspect of the mechanism finds precedent in the stoichiometric deprotonation of cationic rhodium(III) dihydrides to furnish neutral rhodium(I) monohydrides (Eq. 2). The net transformation (H2 + M - X - M - H + HX) is equivalent to a formal heterolytic activation of elemental... 

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