Allyl bromide coupling with Grignard reagents

Asymmetric Coupling Reactions of Chiral Grignard Reagents Derived from Ephedrine Derivatives. Asymmetric coupling reactions of Allyl Bromide and chiral Grignard reagents derived from ephedrine methyl ether in the presence of Copper(I) Iodide (10 mol %) followed by oxidation affords optically active homoallyl alcohols with 60% ee (eq 12). ... 

The 2-pyridyl group couples readily with allylic groups in the reaction of allylic pyridylsulfoxide (84) with Grignard reagents, such as phenylmagnesium bromide. ... 

Allylic alcohols do not react with alkyl- and aryl-Grignard reagents [90]. However, Swierezewski [91] reported that methyl-, phenyl-, and benzylmagnesium bromides reacted with allylic alcohols in the presence of a catalytic amount of NiCl2(PPh3)2 to give either a mixture of SN2/SN2 -coupled products, or when Ri or R2 is equal to phenyl, to the sole Sn2 compound [Eq. (91) and Table 23]. The same selectivity has been observed by Wenkerl in similar conditions [92]. 

Almost exclusive 5, 2 selectivities were observed with Fe" and Ni" catalysts (see Table 24, entries 4, 5, 8, 9), whereas Ti, Cr", Co", and Mn" reacted slowly with a poorer selectivity (see entries 13, 6, 7). These remarkable selectivities toward the SN2-coupling products observed with Ni and Fe catalysts have been observed for the coupling reaction of various Grignard reagents (methyl-, isopropyl-, benzyl-, vinyl-, phenylmagnesium bromides) with primary allylic diphenylphosphates, but in moderate yields with Ni(acac)2, and good yields with Fe(acac)3-... 

Scheme 7 displays a possibility of the synthesis of chiral 2-arylpropionic acids via the oxidative tranformation of (7 )-3-aryl-l-butenes. The requisite chiral olefins may be obtained by transition metal-catalyzed asymmetric coupling between a benzylic Grignard reagent and vinyl bromide (93 % optical yield) [28] or, more attractively, asymmetric hydrovinylation of an aromatic olefin with ethylene. The asymmetric combination of styrene and ethylene, giving the adduct 25 in 95 % ee, has been performed on a 10-kg scale with a dinuclear Ni catalyst formed from ( -allyl)NiCl2 and a unique chiral dimeric aminophosphine obtainable from (/ )-myrtenal and (5)-l-phenylethylamine [7a],... 

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