Asymmetric α‐Azidation Reaction of β‐Ketoesters Catalyzed by Chiral Tin Alkoxides

A catalytic enantioselective α‐azidation reaction of β‐ketoesters with an azidated hypervalent iodine reagent was achieved by using an (R)‐BINOL‐derived chiral tin dibromide possessing 4‐t‐butylphenyl groups at the 3‐ and 3’‐positions as the chiral precatalyst in the presence of sodium ethoxide and ethanol. Optically active α‐azido‐β‐ketoesters having a chiral tertiary carbon were obtained in moderate to high yields under the influence of the chiral tin diethoxide generated in situ. An efficient catalytic enantioselective α‐azidation reaction of β‐ketoesters with an azidated hypervalent iodine reagent is described. The use of in situ generated chiral tin diethoxide as the chiral catalyst enables the synthesis of α‐azido‐β‐ketoesters having a chiral tertiary carbon with up to 59% ee.