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. [References: 80]