Epoxides with organocopper reagents

For a review of the reactions of vinylic epoxides with organocopper reagents, see Marshall Chem. Rev. 1989, 89. 1503-1511. 

Organocopper reagents, 207 of cyclopropanes Dimethyl sulfoxide, 124 Lead tetraacetate, 155 of epoxides (see also Rearrangement reactions, Reduction reactions) with organocopper reagents... 

In general, Sn2 displacement on cyclic vinyl epoxides by organocopper reagents has been found to proceed with inversion anti pathway). However, acyclic vinyl epoxides can react via either s-cis or... 

Substituted epoxides are attacked by organocopper reagents at the least hindered carbon atom and form alcohols (C.R. Johnson, 1973A). With a, 9-unsaturated epoxides tram-allylic alcohols are produced selectively by 1,4-addltion (W. Carruthers, 1973 G.H. Posner, 1972). 

The organocopper reagents prepared in this way cleave epoxides in high yield with substitution of the alkyl group at the less hindered site. This cleavage has been used to effect intramolecular cyclization (second example). 

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. 

Scheme 57 illustrates an example of this process coupling of the lithio reagent derived from vinyl stannane 237 with epoxide 242 leads to the C-disaccharide derivative 243 in good yield. A double transmetallation to give an organocopper reagent 244 can facilitate the C-glycosylation reaction with allyl halides [80] (Scheme 58). 

Mukerji et al. has reported the regioselective alkylation of epoxides with the ate reagent MeLi/Ln(btsa)3 (Eq. 26) [290]. The stereoselectivity of the alkylation reaction of styrene oxide and butadienoxide is complementary to that of organocopper reagents. 

The ring opening of epoxides with carbon nucleophiles represents a Scheme 2.21 useful way of making C-C bonds. Grignard, organolithium and organocopper reagents and alkali metal acetylides have all been used for this purpose. This type of reaction has been used to form carbocyclic systems. 

I.5.2.4.5. Although first reported in 1970, the Sn2 addition of organocopper reagents to vinyl epoxides was not further investigated until nearly a decade later. In the past 10 years, research efforts have concentrated primarily on rigid cyclic systems, which exhibit a pronounced preference for anti-Ss2 reactivity. The stereospecificity of the reaction has been exploited to introduce steroidal side chains with the proper exocyclic stereochemistry. ... 

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