Intramolecular [2+2] Cycloadditions of Keteniminium Salts Derived from a- and b-Amino Acids. A Route to Azabicyclic Ketones

Unsaturated (-tosylaminoketeniminium s a l t s generated i n s i t u from a -and -5-aminoamides r e a d i l y underwent intramolecular [2+2] cycloadditions t o give azabicyclic ketones i n good y i e l d s .Intramolecular [ZtZ] cycloadditions o f ketenes and keteniminium s a l t s have recently been shown 1 t o be valuable reactions f o r t h e stereocontrolled synthesis of p o l y c y c l i c molecules .The preparat i o n of 3-azabicyclo[3.Z.O]heptenones from &unsaturated iminoketenes i s an i l l u s t r a t i o n of the 2 p o t e n t i a l o f the method f o r t h e synthesis o f heterocyclic compounds .