Hydroxy ethers

Other reactions involving the hydrogen atom of the hydroxyl group in ethyl alcohol include the opening of epoxide rings to form hydroxy ethers. 

Throughout the 1990s a large portion of the research and development effort for hot melt adhesives focused on developing adhesives that are either environmentally friendly or functional [69,81,82]. Environmentally friendly attributes include biodegradability, water dispersibility (repulpability), renewability, and water releasability. Biodegradable adhesives have been developed based on starch esters [83-86] and polyesters such as poly (hydroxy butyrate/hydroxy valerate) [87], poly(lactide) [88-91], and poly(hydroxy ether esters) [92-94]. All but the... 

The acetal can also be cleaved with DDQ (CH2CI2, H2O, 66% yield) to afford the monobenzoate. Treatment with DIBAL (CH2CI2, 0°, 91% yield) affords the hydroxy ether. Treatment of a 3,4-dimethoxybenzyl ether containing a free... 

The 2,3-epoxy alcohols are often obtained in high optical purity (90% enantiomeric excess or higher), and are useful intermediates for further transformations. For example by nucleophilic ring opening the epoxide unit may be converted into an alcohol, a /3-hydroxy ether or a vicinal diol. 

Nucleophilic addition of an alcohol to the carbonyl group initially yields a hydroxy ether called a hemiacetal, analogous to the gem diol formed by addition of water. HcmiacetaJs are formed reversibly, with the equilibrium normally favoring the carbonyl compound. In the presence of acid, however, a further reaction occurs. Protonation of the -OH group, followed by an El-like loss of water, leads to an oxonium ion, R2C=OR+, which undergoes a second nucleophilic addition of alcohol to yield the acetal. The mechanism is shown in Figure 19.12. 

This reaction is analogous to 10-7. It may be acid (including Lewis acids),base, or alumina catalyzed, occur with electrolysis, and may occur by either an SnI or Sn2 mechanism. Many of the P-hydroxy ethers produced in this way are valuable solvents, for example, diethylene glycol, Cellosolve, and so on. Reaction with thiols leads to hydroxy thioethers. Aziridines can similarly be converted to P-amino ethers. 

Hydroxy ethers can give cyclic acetals, for example,... 

Diols or (3-hydroxy ethers are particularly useful substrates for fragmentation. If the diol or hydroxy ether is converted to a monotosylate, the remaining oxy group can promote fragmentation. 

A highly useful and important regioselective reduction of substrate 84 leads to a mixture of 3-hydroxy ethers 85 and 86 in a 32 1 ratio (Eq. 306). Compound 85 is further converted to the anti-influenza drug oseltamivir phosphate, better known as Tamiflu .498... 

Chiral acetals/ketals derived from either (R,R)- or (5,5 )-pentanediol have been shown to offer considerable advantages in the synthesis of secondary alcohols with high enantiomeric purity. The reaction of these acetals with a wide variety of carbon nucleophiles in the presence of a Lewis acid results in a highly diastereoselective cleavage of the acetal C-0 bond to give a /1-hydroxy ether, and the desired alcohols can then be obtained by subsequent degradation through simple oxidation elimination. Scheme 2-39 is an example in which H is used as a nucleophile.97... 

Cyclic acetals. In combination with iodine, this reagent resembles lead tetraacetate in the ability to generate alkoxy or aminyl radicals (12,243) under thermal or light activation. This radical oxidation can be used to convert p- or y-hydroxy ethers into dioxolanes or dioxanes.4... 

Figure 3.1 Types of hydrogen bond in order of relative strength (from the left hydroxy-ether, hydroxy-amine and imino-amine)...

EGA-catalyzed ring opening of epoxides, (14), is one of the most-studied catalytic EGA reactions. The proper choice of solvent and supporting electrolyte allows selective formation of a ketone, an allylic alcohol, an acetonide, or an a-hydroxy ether. Scheme 7. 

The results from our work on the reaction of propylene oxide with cobalt carbonyl and base in methanol are given in Table VIII. Several base/metal oxide combinations were evaluated under mild reaction conditions. The difference in activity between the bases was not as pronounced as that observed in the reaction with benzyl halides with the exception of potassium methoxide which, when used alone, gave exclusively the hydroxy ether resulting from methoxide addition to the epoxide ring. However, the activity of sodium... 

Soil. Metabolites of endosulfan identified in seven soils were endosulfan diol, endosulfanhydroxy ether, endosulfan lactone, and endosulfan sulfate (Martens, 1977 Dreher and Podratzki, 1988). These compounds, including endosulfan ether, were also reported as metabolites identified in aquatic systems (Day, 1991). In soils under aerobic conditions, p-endosulfan is converted to P-endosulfan alcohol and p-endosulfan ether (Perscheid et al., 1973). Endosulfan sulfate was the major biodegradation product in soils under aerobic, anaerobic, and flooded conditions (Martens, 1977). In flooded soils, endolactone was detected only once whereas endodiol and endohydroxy ether were identified in all soils under these conditions. Under anaerobic conditions, endodiol formed in low amounts in two soils (Martens, 1977). Indigenous microorganisms obtained from a sandy loam degraded p-endosulfan to endosulfan diol. This diol was converted to endosulfan a-hydroxy ether and trace amounts of endosulfan ether and both were degraded to endosulfan lactone (Miles and Moy, 1979). 

Synonyms AI3-01236 BRN 1098271 CCRIS 2294 Cellosolve Cellosolve solvent Dowanol 8 Dowanol EGEE EINECS 203-804-1 Ektasolve EE Ethyl cellosolve Ethylene glycol ethyl ether Ethylene glycol monoethyl ether Glycol ether EE Glycol monoethyl ether Hydroxy ether Jeffersol EE NCI-C54853 NSC 8837 Oxitol Polysolv EE RCRA waste number U359 Solvid UN 1171. 

Hydroxy-2,3-epoxypropane, see Glycidol Hydroxy ether, see 2-Ethoxyethanol... 

Endosulfan-a-hydroxy ether, see p-Endosulfan, Endosulfan sulfate... 

Along these lines, Jacobsen and co-workers <99AG(E)2012> published an interesting enantioselective cyclization of meso epoxy alcohols which were catalyzed by the cobalt(UI)salen complex 69. Thus, epoxy alcohol 70 was converted to the chiral bicyclic hydroxy ether 71 in 96% yield and 98% ee. 

In the condensation of diols, halogenated alcohols, amino alcohols, cyclic hydroxy ethers, or other bifunctional hydroxy compounds with carbodiimides, 5-, 6-, and 7-membered 1,3-O-N- or l,3-7V,7V-heterocyclics are obtained [14]. 

Related to this process is the ring cleavage reaction of tetrahydrofurans and tetrahy-dropyrans with mixed hydride reagents, e.g. LiAlH4-AlCl3, which provides a route to hydroxy ethers (651 Scheme 150) (65JOC2441, 2448). 

As mentioned in Section 10.6.2, synthesis of 1-hydroxyethylene peptides can be initiated by adding a ferf-butoxycarbonyl N-protected a-amino aldehyde to an optically active Grignard reagent (Scheme 7)J11-13 This reaction affords a diastereomeric mixture of the C4 epimers of the hydroxy ether in good yields. In most cases the mixture is enriched in the 45-epimer and the epimers are readily separable. The yields and the ratios of the resulting 45- and 4R-epimers obtained from several examples of this reaction are summarized in Table 1. When this reaction was attempted with the aldehyde prepared from Aa,Ae-bis-tert-butoxycarbonyl-protected Lys, the desired product was not obtained. The anion of the Lys Ne-tert-butoxy-carbonylamino group probably reacts with the aldehyde to form a cyclic aminol that does not... 

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