Stereo- and Regiochemistry in the (Asymmetric) Cycloaddition Reaction of 5-Chloro-2(1H)-pyrazinones with Cyclic and Monosubstituted Alkenes and with a N-Acryloyl Substituted Chiral Auxiliary.

Abstract The cycloaddition of 5-chloro-2(1 H )-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 1 H 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 (4 S )-4-isopropyl-1-methyltetrahydro-2 H -imidazol-2-one, largely depend on the electron donating or attracting properties and size of the 3-substituents of 1 .