Epoxide with allylmagnesium bromide

In 1974, Vermeer et al. described formation of allenic alcohols 61 by the reaction of alkynyl epoxides 60 with Grignard reagents in the presence of 10mol% of Cul (Scheme 3.33) [71]. In the absence of Cul, a complicated mixture of products was obtained. Furthermore, the Cu-catalyzed reactions exhibited higher yields and higher selectivity than analogous reactions of alkynyl epoxides with lithium dialkylcup-rates [72], This method was applied to a reaction of allylmagnesium bromide with an alkynyl epoxide [73]. 

Thus, the reaction of allylmagnesium bromide with epoxide 275 in FHF gave P-C-D-glucopyranoside 278 in a 75 % yield [217]. It has been also found that the addition of ZnCl2, Li2CuCl4, and Yt(OTf)3 increased the yield of the reaction by 9-15 % [218]. However, the use of other Lewis acids, such as Cul, CuBrSMc2, and Bp3.Et20, caused the opposite effect [218]. The influence of the Lewis acid on stereoselectivity of these reactions has not been studied. 

Thus, the reaction of glycal epoxides with strong nucleophiles, such organocuprates, allylmagnesium bromide, and allyllithium, did not require the use of Lewis acid and proceeded with the formation of l,2-tra s-C-glycosides. 

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