1,3-Dipolar cycloaddition of nitrones with phenylvinyl sulfone. An experimental and theoretical study

The addition of three nitrones to phenylvinylsulfone, 1, has been studied. The stereochemistry previously established by two-dimensional NMR techniques was confirmed by X-ray crystal structure determination. Theoretical studies made us propose that this reaction is not purely regioselective, but by controlling the substituents of nitrone and temperature the regioselectivity increases.

The addition of three nitrones to phenylvinylsulfone has been studied.Figure optionsDownload as PowerPoint slide

(3R,3aR,4S,5R)-3-Phenylsulfonyl-4,5-isopropylidenedioxy-hexahydropyrrolo[1,2-b]isoxazoleC15H19NO5SEe,de: >95% (NMR)[α]D = +11.2 (c 0.7, CHCl3)Source of chirality: natural productAbsolute configuration: (3R,3aR,4S,5R)

(3S,3aR,4S,5R)-3-Phenylsulfonyl-4,5-isopropylidenedioxy-hexahydropyrrolo[1,2-b]isoxazoleC15H19NO5SEe,de: >95% (NMR)[α]D = +22.5 (c 1.4, CHCl3)Source of chirality: natural productAbsolute configuration: (3S,3aR,4S,5R)

(2R,3aS,4S,5R)-2-Phenylsulfonyl-4,5-isopropylidenedioxy-hexahydropyrrolo[1,2-b]isoxazoleC15H19NO5SEe,de: >95% (NMR)[α]D = +155.0 (c 0.9, CHCl3)Source of chirality: natural productAbsolute configuration: (2R,3aS,4S,5R)

(2S,3aS,4S,5R)-2-Phenylsulfonyl-4,5-isopropylidenedioxy-hexahydropyrrolo[1,2-b]isoxazoleC15H19NO5SEe,de: >95% (NMR)[α]D = −130.5 (c 1.6, CHCl3)Source of chirality: natural productAbsolute configuration: (2S,3aS,4S,5R)

(3R,3aR,4S,5S)-4,5-Bis(benzyloxy)-3-phenylsulfonyl-hexahydropyrrolo[1,2-b]isoxazoleC26H27NO5SEe,de: >95% (NMR)[α]D = +84.3 (c 0.9, CHCl3)Source of chirality: natural productAbsolute configuration: (3R,3aR,4S,5S)

(3S,3aR,4S,5S)-4,5-Bis(benzyloxy)-3-phenylsulfonyl-hexahydropyrrolo[1,2-b]isoxazoleC26H27NO5SEe,de: >95% (NMR)[α]D = +58.0 (c 0.3, CHCl3)Source of chirality: natural productAbsolute configuration: (3S,3aR,4S,5S)

(2R,3aS,4S,5S)-4,5-Bis(benzyloxy)-2-phenylsulfonyl-hexahydropyrrolo[1,2-b]isoxazoleC26H27NO5SEe,de: >95% (NMR)[α]D = +90.5 (c 0.2, CHCl3)Source of chirality: natural productAbsolute configuration: (2R,3aS,4S,5S)