Stereoselective Synthesis of Nitrogen-Containing Compounds from Enamines

The
domino reaction of enamines, electrophiles (N-sulfonylimines, N-tosylisocyanate, or diethyl azodicarboxylate),
and trichlorosilane provided trans-amines (trans/cis = > 99:1 to 96:4). Meanwhile,
the sequential imino ene-type reaction of enamines and electrophiles/NaBH3CN reduction afforded cis-amines (trans/cis = 1:>99 to 15:85). The reversal
of selectivity is discussed on the basis of diastereofacial selection
of the plausible iminium ion intermediates. For the domino reaction
of cyclic enamines and cyclic imines, high enantioselectivity (er
= 95.7:4.3 to 99.9:0.1) was achieved by utilizing chiral Lewis base
catalysts.