Epoxides, reaction with

Vinylic organocuprates, prepared by transmetallation of vinylic tellurides with Bu (2-Th)Cu(CN)Li2, are highly reactive towards simple epoxides.  

The table, which collects representative examples, shows that monosubstituted epoxides afford homoaUyhc alcohols resulting from the attack to the less substituted carbon atom (runs 1, 5 and 7). HomoaUyhc alcohols are useful intermediates in several important total synthesis. Disubstituted epoxides fail to react (run 4). Styrene oxide leads to a mixture of homoaUyhc alcohols (run 2) and ally lie epoxides give mixture of 1,2- and 1,4-opening product, with predominance of the 1,4 product (run 3, 6 and 8). 

Vinylic cyanocnprates, prepared from vinylic tellnrides, react with bromoalkynes giving conjugated (Z)-enynes and (Z)-enediynes.  

Reaction with bromoalkynes (typicalprocedure). The butyltelluroenine (R, = n-meth- 

Grignard reagents react with epoxides to form a new carbon-carbon bond and open the three-membered ring, but there are two electrophilic carbon atoms. The final product after hydrolysis is an alcohol. The Grignard reagent attacks the less hindered carbon in an Sn2 like reaction. 3 If the carbons of the epoxide moiety are primary or secondary, attack can occur at either carbon leading to a mixture of alcohol products. 

Chapter 8. Nucleophilic Species That Form Carbon-Carbon Bonds 

When 2-ethyloxirane reacts with methyl magnesium bromide, attack at the primary carbon gave 3-pentanol with only trace amounts of attack at the secondary carbon. When the epoxide has substituents that provide 

If the epoxide moiety is attached to a tertiary carbon, cationic rearrangements can lead to significant amounts of rearranged product. The cationic intermediate generated from the epoxide and MgX2 does not 

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The most important Lewis bases are tertiary amines or polyamines converted into tertiary amines upon reaction with epoxide groups. 

In the reaction with epoxides, y-hydroxysulfones are obtained278-280. For example, Kondo and coworkers279 synthesized various (5-lactols 226 by treating sulfone acetals 225 with terminal epoxides as shown below. Dilithiated phenylsulfonylmethylene reacted with haloepoxide and afforded 3-(phenylsulfonyl)cycloalkanols281. Treatment of y, 5-epoxysulfones 227 and 229 with n-butyllithium resulted in cyclization to form cyclopropane derivatives 228 and bicyclobutane 230, respectively282. 

Reaction with epoxides gives the dangerously unstable and explosive mixed nitrate-perchlorate diesters, such as 1,2-ethanediyl nitrate perchlorate from ethylene oxide. 

Activation of C—Zr bonds as electrophiles with Ag salts has also been applied to the reaction with epoxides (Scheme 1.33) [62—64]. In fact, the reaction has been shown to involve isomerization of epoxides to aldehydes and is therefore very closely related to that shown in Scheme 1.31. 

Titanium enolates.1 This Fischer carbene converts epoxides into titanium enolates. In the case of cyclohexene oxide, the product is a titanium enolate of cyclohexanone. But the enolates formed by reaction with 1,2-epoxybutane (equation I) or 2,3-epoxy butane differ from those formed from 2-butanone (Equation II). Apparently the reaction with epoxides does not involve rearrangement to the ketone but complexation of the epoxide oxygen to the metal and transfer of hydrogen from the substrate to the methylene group. 

Sn2 Reactions with epoxides and aziridines are also synthetically useful. An example of epoxide cleavage with an organocopper reagent with sp carbon moieties is the enantioselective synthesis of (3S, 4S)-4-methyl-3-heptanol (53), an elm bark beetle (Scolytus multistriatus) pheromone [42]. The chiral epoxy oxazolidine 51 [43], prepared from (R)-phenylglycinol, reacted with a propylmagnesium bromide-derived cuprate at —70 °C to afford the oxazolidine 52 in 74% yield (Scheme 9.12). Compound 52 was converted into the target molecular 53 by conventional procedures. 

Sn2 substitution reactions of alkyl halides with hard nucleophiles such as alkyl anions can be achieved most readily with the aid of organocopper chemistry [95]. Sn2 reactions with epoxides and aziridines are also synthetically useful [96]. The... 

Reactions with epoxides are also successful, giving the corresponding hydroxy tel-lurides. ... 

Cleavage of epoxidesThe aiiion (2) of 1 reacts with carbonyl compounds to give a,/(-unsaturated nitriles and LiOSi(CH3)3, as expected.2 The reaction with epoxides is unexpected the products are y-trimethylsilyloxynitriles, which are useful precursors to -/-lactones (equation I). The formulation indicates that a 1,4-migration of the trimethylsilyl group is involved.2... 

Coupling our own methodology with research developed by Wender et al.25 allowed us to devise a five-step sequence for the preparation of the cyclialkylation precursor 63 (Scheme 5.6). In the first step, the organolithium species 60 derived from isopropyl-veratrole24 was used to prepare cyclohexenone 61 through reaction with epoxide 59.25 The... 

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