Yamamoto reagent

Stereoselective substitution reactions of chiral dienyl electrophiles have also been carried out. In analogy to the copper-promoted 8 2 reactions of simple allylic electrophiles [3], the corresponding 8 2 (1,3) substitutions of dienyl carbonates [43] have been reported to proceed with high anti selectivity. Interestingly, treatment of chiral dienyl acetal 63 with the Yamamoto reagent PhCu BFs gave rise to the formation of a 1 3 mixture of the anti-S l substitution product 64 and the syn-Sn2" (1,5) substitution product 65 (Eq. 4.28) [44]. A mechanistic explanation of this puzzling result has yet to be put forward, however. 

Whereas these and other reports did not indicate the possibility of 1,4-cuprate additions to activated dienes, Yamamoto and co workers" showed in their seminal contributions that this is indeed feasible while the reaction of methyl sorbate with the Gilman cuprate M-Bu2CuLi provided exclusively the 1,6-addition product, the reagent formed from butylcopper and the Lewis acid boron trifluoride led to the 1.4-adduct as the major product (equation 15). The synthetically veiy useful organocopper compounds RCu have been named Yamamoto reagents. In certain cases, the regioselectiv-... 

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