Preparation of Pyrrolidine-Based PDE4 Inhibitors via Enantioselective Conjugate Addition of α-Substituted Malonates to Aromatic Nitroalkenes
作者:Paul J. Nichols、John A. DeMattei、Bradley R. Barnett、Nicole A. LeFur、Tsung-Hsun Chuang、Anthony D. Piscopio、Kevin Koch
DOI:10.1021/ol060398p
日期:2006.3.1
[reaction: see text] The enantioselective conjugateaddition of alpha-substituted malonates to aromatic nitroalkenes generates a stereocenter at the carbon bearing the aromatic group and an adjacent prochiral center from the alpha-substituted malonate. Nitro reduction followed by diastereoselective cyclization provides pyrrolidinones with two contiguous stereocenters, one of which is quaternary. This
Supported bifunctional thioureas as recoverable and reusable catalysts for enantioselective nitro-Michael reactions
作者:José M Andrés、Miriam Ceballos、Alicia Maestro、Isabel Sanz、Rafael Pedrosa
DOI:10.3762/bjoc.12.61
日期:——
The catalytic activity of different supported bifunctional thioureas on sulfonylpolystyrene resins has been studied in the nitro-Michael addition of different nucleophiles to trans-β-nitrostyrene derivatives. The activity of the catalysts depends on the length of the tether linking the chiral thiourea to the polymer. The best results were obtained with the thiourea derived from (L)-valine and 1,6-hexanediamine. The catalysts can be used in only 2 mol % loading, and reused for at least four cycles in neat conditions. The ball milling promoted additions also worked very well.
A series of chiral polysulfonate cyclohexyldiamine-Ni(II) catalysts were prepared via sulfur (VI) fluoride exchange click-reactions. The catalysts exhibited good catalytic activity and enantioselectivity in the Michaeladdition of malonates to nitroalkenes. The excellent recyclability of the catalysts was demonstrated via the reuse of the privileged catalyst 7a for ten times. The results provide a
chemical modification of a chiraldiamineligand may produce a robust and recyclable enantioselective catalyst. Metallopolymers based on chiral cyclohexyldiamine‐containing ditopic ligands and nickel(II) complexes have been readily prepared and applied in catalytic enantioselectiveMichaeladditions of 1,3‐dicarbonyl compounds to nitroalkenes. High yields and good enantioselectivities have been obtained and