Alcohols reaction with epoxides

REACTIONS WITH ALCOHOLS, PHENOLS AND EPOXIDES Alcohols... 

For the asymmetric epoxidation reaction, dry alcohol-free dichloromethane (the use of dichloromethane stabilized with methanol must be avoided) is usually the solvent of choice It is inert to the reagents, has good solvent power for the components of the reaction, and supports good epoxidation rates. A fortunate consequence of the asymmetric epoxidation process is that ligation of the allylic alcohol to the Ti center aids in solubilization of the substrate. Substrates that normally may be only modestly soluble in the above-mentioned solvents will be brought into solution as they complex with the Ti-tartrate catalyst. 

Because of its very short lifetime, no spectroscopic observations of 1 were possible even at low temperature. However, we provided evidence for the transient formation of 1 by trapping reactions with alcohols, diols, amines,methyl iodTtle, epoxides, dienes, ketones. Some examples are as follows. 

In the presence of BiCl3, epoxides undergo ring-opening addition reactions with alcohols, acetic acid, and water to afford ct-alkoxy, ct-acetoxy, and a-hydroxy alcohols, respectively (Equation (81)).137 In the presence of BiCl3 or... 

In epoxidation reactions allyl alcohol can act as a prochiral alkene. Enantio-merically pure glycidol isomers (see Table 1.1) may be used to make S-propanolol 9.61, a drug for heart disease and hypertension. The mechanistic details of the epoxidation reaction with V5+ and Mo6+ complexes as catalysts were discussed in Section 8.6. The basic mechanism of epoxidation reaction, the transfer of an oxygen atom from f-butyl hydroperoxide to the alkene functionality, remains the same. 

All the reactions of epoxidic groups with alcohols or water, in excess, are SN-1 reactions of the type shown in reaction 17.23, having as intermediates organic cations, such as oxonium ions and carbo cations. 

Scheme 11.2 Formation of oxonium ions by the addition of protons to epoxides and their subsequent reaction with alcohols.

Reaction of Epoxidized Esters with Alcohols. Alcoholysis study of epoxidized RME with ethanol and heptanol was condueted to determine the best eleavage conditions of the oxirane group acid catalysts (zinc chloride, PTSA) and a basic catalyst (sodium methylate) were tested. The results are reported in Tables 9 and 10. As expected, no cleavage of the oxirane group occurred when no catalyst or basic catalyst was used at temperatures <100°C. 

The ring-opening process of Equation 8.45 is, of course, simply the reverse of the process by which oxiranes (oxacyclopropanes, epoxides) are formed from halohy-drins (e.g., see item 3,Table 7.6). Further, as written, the processes shown in Schemes 8.90-8.92 are reversible and thus, at least in principle, carbonyl compounds can be converted to enol ethers, acetals (and ketals), and orthoesters. However, while acetals and ketals readily form from alcohols and acids under dehydrating conditions (Chapter 9) and esters undergo exchange reactions with alcohols in the... 

Shechter and Wynstra deduced that tertiary amines initiate epoxide polymerization by addling to the epoxide, which is then followed by a reaction with alcohol ... 

Tertiary amines are believed to initiate epoxide polymerization by their addition to epoxide, followed by reaction with alcohol. 

Prepared by epoxidation of styrene with per-oxyelhanoic acid. Reactions are similar to those of aliphatic epoxides (s e, e.g. ethylene oxide). Reacts with alcohols to give mono-ethers, e g. PhCH(0Me)CH20H. Phenols give resins. 

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