The Chemistry of Pericyclic Reactions and Their Application to Syntheses of Heterocyclic Compounds

Chemical reactivity of dihydropyrazine derivatives. Cycloaddition behavior toward ketenes

The cycloaddition behavior of dihydropyrazines toward ketenes was investigated using single-crystal X-ray structures of the cycloadducts and density functional theory (DFT) calculation data. The reaction proceeds via a stepwise pathway involving an orientation complex prior to formation of the betaine intermediate. This is followed by electrocyclization to afford the 1 : 1 and 1 : 2 adducts bearing beta-lactam ring(s).