Diversity-Oriented Asymmetric Catalysis (DOAC): Stereochemically Divergent Synthesis of Thiochromanes Using an Imidazoline–Aminophenol–Nickel-Catalyzed Michael/Henry Reaction

The
(S,S)-diphenylethylenediamine-derived
imidazoline–aminophenol–Ni complex catalyzed tandem
asymmetric Michael/Henry reaction of 2-mercaptobenzaldehydes with
β-nitrostyrenes to give the corresponding (2S,3R,4R)-2-aryl-3-nitrothiochroman-4-ols
in up to 99% diastereoselectivity with 95% ee was demonstrated in
diversity-oriented asymmetric catalysis. Reduction of the nitro group
of the chiral thiochromanes gave a new series of (2S,3R,4R)-3-amino-2-arylthiochroman-4-ols
with retention of the strereoselectivity.