| Abstract
| - The results from this study show that, contrary to the acceptedmechanism, the reaction ofbenzaldehyde-1-d with B-Ipc-9-BBN involves a different conformation ofthe reagent and it doesnot proceed, as previously assumed, through a boat-like transitionstate. The overall reactivity ofthe B-alkyl-9-BBN reagents is determined by the ability ofthe boron center to undergo efficientcoordination expansion during the formation of the charge-dipolecomplex with benzaldehyde. Theexclusive preference toward the (S)-benzyl-1-d alcohol inthe reduction of benzaldehyde-1-d withB-Ipc-9-BBN is governed, also at the charge-complex stage,by preferential orientation of thebenzaldehyde's C−D rather than C−Ph bond against one of theprostereogenic B−CH bonds of the9-BBN moiety that is “gauche” to theC1−C2 bond of the Ipc ring.
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