A new asymmetric approach toward 5-substituted pyrrolidin-2-one derivatives
摘要:
The condensation between a chiral 2-silyloxypyrrole and either achiral or chiral formyl cation equivalents has been studied. The methodology has allowed to build-up 5-substituted pyrrolidin-2-one derivatives with a stereocontrol from good to excellent. The chiral auxiliary located on the silyloxypyrrole showed an intrinsic good level of diastereoface discrimination at C-5. However. the use of a 2-methoxy-3-tosyl-oxazolidine as chiral formylating agent allowed a total stereocontrol in the condensation. A rationale for the observed stereochemical outcome is presented. The stereoselective manipulation of these adducts provided new potentially interesting pyroglutamic aldehyde and prolinal derivatives. whereas treatment with TiCl4 triggered unexpectedly a Pomeranz-Fritsch type intramolecular condensation affording a benzocondensated indolizidinone. (C) 1998 Elsevier Science Ltd. All rights reserved.
A new asymmetric approach towards 2-pyrrolidinones and pyrrolidines: Simple versus double stereodifferentiation
摘要:
The condensation of a chiral 2-silyloxypyrrole derivative with achiral and chiral formyl cation equivalents has been studied for the first time. The methodology allows to build-up pyroglutammic aldehydes and prolinal systems with a stereocontrol from good to excellent. Whereas the chiral auxiliary residing on the pyrrole system shows an intrinsic good level of diastereoface discrimination at C-5, the combined use of a 2-methoxy-3-tosyl-oxazolidine as a chiral formylating agent allows a total stereocontrol of the condensation. A rationale for the observed stereochemical outcome is presented.
The condensation of a chiral 2-silyloxypyrrole derivative with achiral and chiral formyl cation equivalents has been studied for the first time. The methodology allows to build-up pyroglutammic aldehydes and prolinal systems with a stereocontrol from good to excellent. Whereas the chiral auxiliary residing on the pyrrole system shows an intrinsic good level of diastereoface discrimination at C-5, the combined use of a 2-methoxy-3-tosyl-oxazolidine as a chiral formylating agent allows a total stereocontrol of the condensation. A rationale for the observed stereochemical outcome is presented.
A new asymmetric approach toward 5-substituted pyrrolidin-2-one derivatives
The condensation between a chiral 2-silyloxypyrrole and either achiral or chiral formyl cation equivalents has been studied. The methodology has allowed to build-up 5-substituted pyrrolidin-2-one derivatives with a stereocontrol from good to excellent. The chiral auxiliary located on the silyloxypyrrole showed an intrinsic good level of diastereoface discrimination at C-5. However. the use of a 2-methoxy-3-tosyl-oxazolidine as chiral formylating agent allowed a total stereocontrol in the condensation. A rationale for the observed stereochemical outcome is presented. The stereoselective manipulation of these adducts provided new potentially interesting pyroglutamic aldehyde and prolinal derivatives. whereas treatment with TiCl4 triggered unexpectedly a Pomeranz-Fritsch type intramolecular condensation affording a benzocondensated indolizidinone. (C) 1998 Elsevier Science Ltd. All rights reserved.