B-n-Butyl-9-BBN

Reductions with ate complexes of 9-BBN. Japanese chemists have prepared the two ate complexes of 9-BBN (1) and (2) by reaction of B-n-butyl-9-BBN with -butyUithium and methylUthium, respectively. The bridgehead... 

The lithium di-n-butyl ate complex of 9-BBN, prepared [1] from B-n-butyl-9-BBN and n-butyllithium exhibits high stereo-, chemo-, and regioselectivities in the reduction of cyclohexanones. Consequently, both cis- and frans-4-methyl-cyclohexanols are independently obtained from 4-methylcyclohexanone by a mere change in the additives (Chart 26.10 Table 26.33) [2]. 

Selective reduction of t-alkyl halides. The ate complex of B-butyl-9-BBN with n-BuLi selectively reduces tertiary alkyl halides to hydrocarbons in high yield without effect on primary or secondary halides. It does not reduce aryl or vinyl halfdes, but does reduce benzyl and allyl halides. The reduction involves a carbonium ion, and thus can proceed with Wagner-Meerwein rearrangements in certain systems. 

Table 6.16 Comparison of the allenylboration of [A] and [B] with allenylmagnesium bromide, di(n-butyl)-allenylboronate and B-allenyl-9-BBN [4]...

Wang et al [2] have reported that treatment of the readily available 3-(fert-butyl-dimethylsilyl)-l-(trimethylsilyl)-l-propyne [4] with n-butyllithium, followed by B-MeO-9-BBN and 4/3 BFj-OEtj [5] yields B-allenyl-9-BBN. The condensation of B-allenyl-9-BBN with hexanal or benzaldehyde and followed by the elimination step of the Peterson olefination [3] affords the conjugated enynes (Scheme 24.15) [2]. 

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