Epichlorohydrin chloride, epoxidation

The epoxidation is generally conducted in two steps (/) the polyol is added to epichlorohydrin in the presence of a Lewis acid catalyst (stannic chloride, boron triduoride) to produce the chlorohydrin intermediate, and (2) the intermediate is dehydrohalogenated with sodium hydroxide to yield the aliphatic glycidyl ether. A prominent side-reaction is the conversion of aliphatic hydroxyl groups (formed by the initial reaction) into chloromethyl groups by epichlorohydrin. The aliphatic glycidyl ether resins are used as flexibilizers for aromatic resins and as reactive diluents to reduce viscosities in resin systems. 

Jacobsen (1999) has carried out carbomethoxylation of asymmetric epoxides. Thus, the carbomethoxylation of (R)-propylene oxide with CO and methanol yields 92% of (3R)-hydroxybutanoic acid in greater than 99% ee. Similarly, the reaction of (/ )-epichlorohydrin gives 96% of 4-chloro-(3R)-hydroxybutanoic acid in greater than 99% ee. The catalyst consists of dicobalt octacarbonyl and 3-hydroxy pyridine. A continuous process for making enantiomeric 1-chloro-2-propanol has been suggested. With a suitable catalyst propylene reacts with O2, water, cupric and lithium chloride to give 78% of (S)-l-chloro-2-propanol in 94% ee. 

When epichlorohydrin was in the presence of trichloroethylene with chloride ion traces, there was a deflagration. Similar accidents have been described with other epoxidic substances. 

Epichlorohydrin Epoxidized Vegetable Oils Epoxidized Vegetable Oils Octyl Epoxy Tallate Epoxidized Vegetable Oils Butylene Oxide Ethylene Oxide Propylene Oxide Sodium Nitrite Copper Chloride Trichloiofluoromethane Dichlordifluoromethane Monochlorodifluoromediane Nitrobenzene Acetaldehyde Ethane... 

Stephenson has developed a convenient procedure for preparing J-chloro-3-phenoxy-2-propanols from epichlorohydrin nnd phenols, which is economical of reagents and minimizes the formation of undesirable side-products (Eq. 600). He has also greatly extended the applicability of hydrogen chloride transfer for the preparation of epoxides. ... 

In another development, the statin side chain en route to Atorvastatin (Lipitor , Pfizer) is synthesized via the key intermediate alkyl 3-hydroxy-4-cyanobutyrate (Figure 13.17). Instead of the currently practiced six-step route, a much more concise three-step route starts from epichlorohydrin via Cl chain length enhancement by both nucleophilic substitution of chloride and nucleophilic ring opening of the epoxide with cyanide to yield symmetric dicyanoisopropanol. Nitrilase action desymmetrizes the dinitrile intermediate with the creation of a chiral center in C3 to yield (R)-3-hydroxy-4-cyanobutyrate, which is esterified to the key intermediate ethyl (R)-3-hydroxy-4-cyanobutyrate. 

The first type of epoxy product (phenoxypropene oxide) from sodium phenolate and epichlorohydrin was used in 1932 by IG Farbenindustrie but showed too high a volatility. Corresponding derivatives of alkyl-phenols gave excellent results. The condensation product of diisobutyl-phenol was used under the name, stabilizer DBG. The epoxides do not form insoluble metal chlorides like lead compounds. 

Though this reaction looks like a simple SN2 displacement by the naphthyloxide anion on the primary alkyl chloride, there is, in fact, a reasonable alternative—the opening of the epoxide at tire less hindered primary centre followed by closure of the epoxide the other way round. The electrophile is called epichlorohydrin and has two reasonable sites for nucleophilic attack. 

Cellulose can be modified with organostannane chlorides, such as dibutyl or triphenyl derivatives [91,92], or with organotin halides in the presence of bisethylenediamine copper(II) hydroxide [93]. Epoxy-activated cellulose was prepared by reacting cellulose acetate fibers with sodium methoxide, followed by reacting it with epichlorohydrin in DMSO. This epoxy-activated cellulose has proved to be a useful intermediate to react with substances containing active hydrogen, such as amine, amino acid, or carboxylic acids [94], as shown in Fig. 3. Epoxidized cellulose has also been converted to a thiol derivative via reduction of a thiosulfate intermediate [95], and sulfoethylcellu-[ose has been obtained from sodium chloroethanesulfonate [96]. Cellulose... 

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]. 

The epoxidation of alkenes, though, is generally carried out at ambient temperature. This reaction is rapid and selective with unhindered double bonds. Hindered alkenes or those having electron withdrawing groups present in the molecule require somewhat higher temperatures for epoxidation. The oxidation of allyl chloride takes place at 40°C to give a 75% yield of epichlorohydrin (Eqn. 21.2).30... 

The most widely used epoxy resins and adhesives are based on a prepolymer made from bisphenol A and epichlorohydrin. On treatment with base under carefully controlled conditions, bisphenol A is converted into its anion, which acts as a nucleophile in an S142 reaction with epichlorohydrin. Each epichlorohydrin molecule can react with two molecules of bisphenol A, once by S 2 displacement of chloride ion and once by opening of the epoxide ring. At the same time, each bisphenol A molecule can react with two epichlorohydrins, leading to a long polymer chain. Each end of a prepolymer chain has an unreacted epoxy group, and each chain has numerous secondary alcohol groups. 

Two components are required, which are mixed just prior to use. The prepolymer, in which the cross-linkable epoxide functions reside, is made from epichlorohydrin and /s-phenol A. Epichlorohydrin in turn is derived from allyl chloride (Eq. 21.24). 

---