Boranes copper salts

As mentioned in Section 9.12.2.1.1, the boron-zinc exchange can be performed stereoselectively if diisopropyl-zinc instead of diethylzinc is used. For example, hydroboration of the chiral, racemic endocyclic olefin 134 with diethylzinc, followed by twofold transmetallation and electrophilic capture of the resulting copper intermediate with allyl bromide was used for the highly diastereoselective formation of the stereotriad in product 136 (Scheme 35).35,35a 103 QorreSp0nding enantioselective transformations were carried out with chiral boranes and catalytic amounts of copper salts (see Section 9.12.2.2.2).36... 

A common method used for the preparation of bisphosphinoethanes is the reductive coupling of a methyl phosphine oxide or phosphine borane (Scheme 18) using a strong base and copper salts.27 This process occurs with no racemization of the adjacent phosphorus atom. 

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