Efficient Preparation of [2‐ 13 C]‐ and [3‐ 13 C]‐3‐Cyano‐4‐methyl‐3‐pyrrolin‐2‐one

[2‐ 13 C]‐ and [3‐ 13 C]‐3‐cyano‐4‐methyl‐3‐pyrrolin‐2‐one have been prepared by a new synthetic route. α,α‐Dimethoxy ketones react with bifunctional molecules in an extended Knoevenagel reaction. The products of this reaction are converted in a few steps and in high yields into the biologically important 3‐pyrrolin‐2‐ones. This new approach also allows simple stable isotope incorporation at many sites of the ring system. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)