In memory of Dieter Enders
Abstract
Several chiral sulfoxides with a lactam hydrogen-bonding site were prepared and their
photochemical behavior was studied in the presence of xanthone and thioxanthone sensitizers.
While acyclic sulfoxides showed only decomposition, chiral benzothiazinone-1-oxides
with a stereogenic sulfur atom underwent a stereomutation upon irradiation at λ = 366
nm in the presence of catalytic quantities of a xanthone sensitizer. A chiral xanthone
with a 1,5,7-trimethyl-3-azabicyclo-[3.3.1]nonan-2-one backbone was employed in catalytic
quantities (5 mol%) to achieve a deracemization reaction of racemic benzothiazinone-1-oxides
in acetonitrile solution. Five substrates could be successfully deracemized in good
yields and with up to 55% ee .
Key words deracemization - enantioselective synthesis - homogeneous catalysis - photochemistry
- sensitization - sulfoxides