REDUCTION OF ELECTRON-DEFICIENT PYRROLES USING GROUP-I AND GROUP-II METALS IN AMMONIA

The preparation and Birch reduction of a series of electron-deficient pyrroles is described. This methodology allows the synthesis of a vari ety of C-2 substituted 3-pyrrolines double dagger in good to excellent yields, The role of various activating groups (amide, ester, carbamat e and urea) has been examined with regard to both stability under the Birch conditions and ease of deprotection after reduction, In addition , we discovered that the 3-pyrroline skeleton can be oxidised at C-5 w ith chromium trioxide-3,5-dimethylpyrazole to form the 3-pyrrolin-2-on e nucleus. The identity of the Birch reduced products and also of the oxidised 3-pyrrolin-2-ones has been confirmed by X-ray crystallography on two derivatives.