Hydrogen halides epoxides

In the following procedure, use is made of the basic character of epoxides. In the presence of phosphonium salts, ethylene oxide removes hydrogen halide and the alkylidenetriphenylphosphorane is produced. If a suitable carbonyl compound is present in the reaction mixture, its reaction with the in situ generated phosphorane proceeds readily to give the Wittig product. 

Cleavage of epoxides with hydrogen halides Addition of hypohalous acids to alkenes... 

When simple aliphatic epoxides such as propylene oxide react with hydrogen halides, the dominant product has the halide at the less-substituted primary carbon.111... 

The action of hydrogen halides on misoeUaiieocs other ethylene oxides containing polar atoms in the vicinity of the epoxide ring ha been described. Among substances examined in this connexion... 

The course of this reaction was proved by Hilt et al.42> 54 > who used as copolymerization initiators 14C-labelled sodium and potassium benzoate. The activity of the prepared copolymer is due to the labelled and chemically bound initiator anion. This reaction is analogous to the analytic determination of epoxides by hydrogen halides 59 but instead of inactive halogen hydrine generaled according to Eq. (12), an ionic particle capable of initiating copolymerization is formed. 

Nakamura T, Nagasawa T et al (1991) A new catalytic function of halohydrin hydrogen-halide-lyase, synthesis of P-hydroxynitriles from epoxides and cyanide. Biochem Biophys Res Commun 180 124—130... 

Benzyl methyl ether or allyl methyl ethers can be selectively metalated at the benzylic/allylic position by treatment with BuLi or sBuLi in THF at -40 °C to -80 C, and the resulting organolithium compounds react with primary and secondary alkyl halides, epoxides, aldehydes, or other electrophiles to yield the expected products [187, 252, 253]. With allyl ethers mixtures of a- and y-alkylated products can result [254], but transmetalation of the lithiated allyl ethers with indium yields y-metalated enol ethers, which are attacked by electrophiles at the a position (Scheme 5.29). Ethers with ft hydrogen usually undergo rapid elimination when treated with strong bases, and cannot be readily C-alkylated (last reaction, Scheme 5.29). Metalation of benzyl ethers at room temperature can also lead to metalation of the arene [255] (Section 5.3.11) or to Wittig rearrangement [256]. Epoxides have been lithiated and silylated by treatment with sBuLi at -90 °C in the presence of a diamine and a silyl chloride [257]. 

The polymerizable groups include methacryloyl, styrenic, epoxide, vinyl ether, and others, among which the methacryloyl-capped macromonomers are most widely available from vinyl ethers, styrene, and its derivatives. For example, the a-end methacryloyl group can be introduced by the functional initiator method, with the hydrogen halide-adduct of 2-... 

In the reaction of butyllithium or lithium di-isopropylaminc with the Mannich bases derived from hydrogen cyanide, phosphine oxides, and phosphorous esters, as well as from phenols, jhc metal atom is prevalently bound to the CH2—N moiety (313 in big. 119, route b). This intermediate is then allowed to react with halides, epoxides, and other alkylating reagents in order to link an alkyl group to methylene. Under proper conditions, aldehydes, ketones and enamines can be prepared by this method. 

As an alternative practical method, the opening of epoxides by halide ions has often been used for introducing halogens, especially fluorine, into sugar molecules. Sodium iodide, magnesium bromide, and hydrogen halides (HCl, HF) are frequently used as halogen sources [64,65]. 

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