Allyl chloride epoxidation

Catalyst D was used to develop this commercialized allyl chloride epoxidation technology. The recycling of the catalyst in the solvent-free reaction system was studied (Table 17.9). 

TABLE 17.9 Effect of Recycle of Catalyst D on Allyl Chloride Epoxidation°... 

In mosl allylation reactions, only a catalytic amount of CuCN-2LiCl is required [41]. Use of die chiral ferrocenylamine 104 as a catalyst makes enables asymmetric allylation of diorganozinc reagents to be effected witli allylic chlorides iScbeme 2.3G) [78]. Related electropb des such as propargylic bromides [79] and unsaturated epoxides [80] also undergo Su2 -substitution reactions iScbeme 2.37). 

Previous syntheses of terminal alkynes from aldehydes employed Wittig methodology with phosphonium ylides and phosphonates. 6 7 The DuPont procedure circumvents the use of phosphorus compounds by using lithiated dichloromethane as the source of the terminal carbon. The intermediate lithioalkyne 4 can be quenched with water to provide the terminal alkyne or with various electrophiles, as in the present case, to yield propargylic alcohols, alkynylsilanes, or internal alkynes. Enantioenriched terminal alkynylcarbinols can also be prepared from allylic alcohols by Sharpless epoxidation and subsequent basic elimination of the derived chloro- or bromomethyl epoxide (eq 5). A related method entails Sharpless asymmetric dihydroxylation of an allylic chloride and base treatment of the acetonide derivative.8 In these approaches the product and starting material contain the same number of carbons. 

Epoxidation of ally alcohol and allyl chloride—influence of pH... 

The Ni(II) complexes of salen analogues with bipyridine units 36 showed higher catalytic activity than Ni(IIXsalen) in the epoxidation of an electron-deficient olefin, allyl chloride. Their enhanced reactivity was ascribed partially to their higher stability relative to the salen complex (98). 

Activation of allyl chloride to genotoxic substances appears to involve aldehydes, since inhibition of aldehyde dehydrogenase by cyanamide increases the mutagenic activity in Salmonella typhimurium TAIOO on the other hand neither SKF525 nor 1,1,1-tri-chloropropene-2,3-oxide affect the mutagenicity, so that metabolic activation via an epoxide is unlikely (Neudecker Henschler, 1986). 

The oxidations of C5-C8 olefins, allyl chloride, allyl alcohol, and allyl methacrylate with H202 give the corresponding epoxides. Data characterizing oxidations carried out in methanol solvent at an olefin concentration of 0.90 M, in the presence of TS-1 (6.2 g/L), are given in Table V. 

Electron withdrawing groups on the alkene considerably retard the epoxidation. For example, acrylic esters and acrylonitrile are not reactive, while allyl chloride is about one tenth as reactive as propylene towards TBHP/MoVI.240 The epoxidation of alkenes is completely stereoselective eri-alkenes are exclusively transformed into ds-epoxides and (runs-alkenes into trans-epoxides. Oxygen addition to the double bond preferentially occurs from the less shielded face of the substrate, e.g. in the selective epoxidation of terpenes by r-pentyl hydroperoxide (t-amyl hydroperoxide, TAHP) (equations 67 and 68).225... 

The palladium-catalyzed reaction of aryl- and vinyl-tin reagents with stereochemically defined allyl chlorides proceeds with overall retention of configuration, indicating that the second step, entailing interaction of the iT-allylpalladium complex and the organotin, proceeds by transmetallation and reductive elimination (attack at Pd, retention) (equations 166 and 167).142145 Comparable results were obtained with cyclic vinyl epoxides and aryltins.143... 

Electron-attracting substituents in the hydroperoxide increase the rate of epoxidation428, 434 by increasing the electrophilic character of the peroxidic oxygens. With alkylaromatic hydroperoxides, a competing metal-catalyzed heterolytic decomposition of the hydroperoxide can take place. The problem becomes especially important in epoxidations of unreactive olefins such as allyl chloride.434 For example, cumene hydroperoxide affords phenol and acetone,... 

An important recent advance in the area is the demonstration that allyl chlorides readily form allylcopper species upon exposure to highly activated copper ( Rieke copper ). The resultant allylcoppers have been shown to react with a fairly wide range of nucleophiles (ketones, aldehydes, acid chlorides, enones, epoxides [after conversion to the cuprate], imines, and allyl bromides)56. Regiochemical considerations in such substitutions depend upon the cases studied, and are fairly complex. The allylcoppers formed have, in all cases, the least substituted C—Cu bond allyl transfer from these reagents is selective from the imposition of the allyl (enone electrophiles excepted)(equations 41 and 42). The allyl chloride... 

TS-1 exhibits some quite remarkable activities and selectivities in the epoxidation of many substrates. For example, relatively unreactive olefins such as ethene and allyl chloride are epoxidized in high yield under mild conditions using methanol as the solvent.19 As a result of the shape selectivity effect, larger, more reactive olefins such as cyclohexene are epoxidized very slowly (Table 4.2). 

Epoxidation of allyl alcohol and allyl chloride—influence cfpH... 

Epoxidation of Allyl Chloride and other Substituted Olefins... 

Several patents and two papers deal with the epoxidation of allyl chloride [98, 99]. Actually, a process based on TS-1 would represent an environmentally cleaner alternative to current production of epichlorohydrin. In this regard, one study has addressed the cost of commercial hydrogen peroxide with the in situ production of the oxidant, by the use of molecular oxygen and anthrahydroquinone compounds [99]. In a mechanistic study, the kinetic data were interpreted on the basis of Eley-Rideal isotherms, with the rate of reaction being first order on TS-1 and between 0 and 1 on H2O2 and C3H5CI (Equation 18.8) [98]. 

Alkane oxidation to alcohols, aldehydes and ketones has been extensively studied and it was found that the smaller linear alkanes show higher turnovers than the longer linear, branched and cyclic alkanes [81]. Although the turnover numbers are found to increase with the addition of methanol as a co-solvent, the general role of the co-solvent in selectivity is still not clear. Catalytic epoxidations of relatively inert alkenes such as propylene and allyl chloride were found to be facile under mild... 

Although a terminal epoxide seems to be more reactive than a primary alkyl tosylate [Eq. (32) 79], primary alkyl tosylates [80] and iodides [81,82], allyl chlorides [45], or a terminal epoxide [69] could be selectively displaced with an internal epoxide moiety being intact [Eq. (33) 81]. 

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