RING TRANSFORMATION OF FURFURAL INTO AN UNUSUAL BICYCLIC SYSTEM - CHARACTERIZATION AND DYNAMIC STEREOCHEMISTRY OF RBONYL-6,7-DIAZA-8-OXABICYCLO[3,2,1]OCT-3-EN-2-ONE

2-Formylthiophene and 3-formylindole react with diethyl azodicarboxyla te to give simple products derived from reactions on the formyl group whereas 2-formylfuran reacts to give the unexpected bicyclic title com pound. H-1 and C-13 NMR Studies indicate that this compound undergoes a series of three dynamic conformational changes over the temperature range 50 to -90 degrees C which are ascribed to slow rotation about th e exocyclic carbamate bonds and hindered bridge inversion. (C) 1997 El sevier Science Ltd.