Butylborane, tri-sec

Lithium and magnesium chelates have no effect on the stereoselection of this reduction. Triisobutylborane is somewhat more effective than n-butylboranc no reduction occurs if tri-.sec-butylborane is used. 

This reducing agent is prepared in quantitative yield by the reaction of lithium tri-methoxyaluminum hydride (LTMA, 1, 625 2, 252-253) with the highly hindered tri-sec-butylborane in THF at 25°. Aluminum meihoxide is also formed, but since it is inert, the reaction mixture can be used directly. ... 

---