Diastereoselective LiAlH4 reduction of chiral ketone hydrazones derived from (R)-(-)-2-aminobutan-1-ol

Various chiral N,N-dialkylhydrazines were prepared in four to five steps from (R)-(-)-2-aminobutan-1-ol 6. They reacted with various prochiral ketones, thus giving the corresponding hydrazones. Reduction of the latter by means of LiAlH4 afforded N,N,N'-trisubstituted hydrazines whose d.e.s were in the range 43-100%. Interestingly, LiAlH4 reduction of the four N-trifluoroethylhydrazones 34 and 38-40 yielded the hydrazines 46 and 48-50, respectively, and with d.e.s = 100% by H-1 and C-13 NMR. (C) 2000 Elsevier Science Ltd. All rights reserved.