Highly stereoselective synthesis of homoallylic amines based on addition of allyltrichlorosilanes to benzoylhydrazones

Allyltrichlorosilanes reacted with benzoylhydrazones in DMF without the use of any catalyst to afford the corresponding homoallylic benzoylhydrazines in good to high yields. The reactions proceeded at 0 degreesC to room tempe rature under mild conditions. In addition, it was found that the reactions tolerated well the steric hindrance of hydrazones and allyltrichlorosilanes . Indeed, ketone-derived benzoylhydrazones reacted with allyltrichlorosilan e smoothly to afford the corresponding N'-tert-alkyl-N-benzoylhydrazines in high yields. In crotylation with (E)- and (Z)-crotyltrichlorosilanes, syn- and anti-adducts were stereospecifically obtained, respectively. These rea ctions. are most likely to proceed via a cyclic chairlike transition state where the R group takes an axial position. When alpha -heteroatom-substitut ed chiral benzoylhydrazones were used, high anti-diastereoselectivities wer e observed. These adducts can be readily converted to homoallylic amines in high yields without epimerization.