Control of regio‐, diastereo‐, and enantioselectivity in the [Ti(OTs)₂(TADDOLato)]‐catalyzed 1,3‐dipolar cycloaddition reaction between 3‐acryloyloxazolidin‐2‐one and nitrones

Abstract

Abstract Catalytic control of regio‐, diastereo‐, and enantioselectivity in the 1,3‐dipolar cycloaddition of 3‐acryl‐oyloxazolidin‐2‐one ( 4 ) with different nitrones 2 by the application of a [TiX 2 (TADDOLato)] complex as the catalyst was developed (TADDOL = α,α,α′,α′‐tetraaryl‐1,3‐dioxolane‐4,5‐dimethanol). In the absence of a catalyst, the 1,3‐dipolar cycloaddition of 4 with 2 proceeded to give a mixture of regioisomers, whereas, in the presence of a catalyst, the regioselectivity of the reaction could be controlled. Three asymmetric [TiX 2 (TADDOLato)] catalysts were tested, and it was found that use of the [Ti(OTs) 2 (TADDOLato)] complex gave complete regioselectivity, high ‘ endo ’‐selectivities (> 90% d.e.), and enantioselectivities corresponding to 48–70% e.e.