Asymmetric transfer hydrogenation of a new N-tosyltetrahydrocarbazole-1-one ester with the Noyori-Ikariya catalyst

: Enantioselective reduction of a new 1-oxotetrahydrocarbazole compound (ethyl 2-(1-oxo-9-tosyl-2,3,4,9-tetrahydro-1 H -carbazol-2-yl)acetate) through asymmetric transfer hydrogenation by using the commercially available Noyori–Ikariya ruthenium catalyst and HCO 2 H/Et 3 N or HCO 2 H/DABCO as the hydrogen source have been investigated. High enantiomeric excesses (up to 96% ee ) and moderate to good yields (24–72%) for corresponding alcohol and lactone compounds have been achieved. Structures of all compounds have been characterized by spectroscopic techniques.