The cycloaddition of 5-chloro-2(1H)-pyrazinones 1 with various dienophiles was used to generate the corresponding 2,5-diazabicyclo[2.2.2]octanes. Following reduction or hydrolysis of the bridged adducts, the regio- and stereochemical structure was determined by analysis of the coupling and NOE patterns in the H-1 NMR spectra. With symmetric dienophiles the endo adducts are formed exclusively. The regiochemistry for the reaction of 1 with methyl acrylate and ethyl vinyl ether, and the asymmetric induction found with the N-acryloyl substituted chiral auxiliary (4S)-4-isopropyl-1-methyltetrahydro-2H-imidazol-2-one, largely depend on the electron donating or attracting properties and size of the 3-substituents of i. (C) 2001 Elsevier Science Ltd. All rights reserved.