Introduction <P>Lithium tri-
sec -butylborohydride (
l -Selectride) is known to be an exceptionally
powerful and highly stereoselective reducing agent. It has been
used for the diastereoselective reduction of the ketones to give
the alcohol,
[
¹-¹0 ]
selective 1,4-reduction
of the enones by conjugate addition of hydride to afford ketones
[
¹¹ ]
[
¹² ]
or alcohols,
[
¹³ ]
conjugate reduction
of exocyclic acrylonitrile derivatives,
[
¹4 ]
reduction
of the double bond
[
¹5 ]
and
iodide.
[
¹6 ]
It was also found
to be an efficient reagent for the desymmetrization of
meso -diesters,
[
¹7 ]
dehalogenation of monohalopyridines,
[
¹8 ]
rearrangement of 5-trimethylsilylthebaine,
[
¹9 ]
reductive cleavage of
exoxides,
[
²0 ]
and deprotection
of
N -carbomethoxy-substituted opioids
to
N -noropioids.
[
²¹ ]
</P><P>Lithium tri-
sec -butylborohydride is
commercially available, but can also be readily prepared by addition
of tri-
sec -butylborane to a tetrahydrofuran
solution of lithium aluminium hydride at room temperature. It is
obtained as colorless solution in tetrahydrofuran.
[
²² ]
</P>
Scheme 1
