1,3-dipolar cycloaddition reactions of benzonitrile oxide to 2(1H)-pyrazinone and its N- and O-methyl derivatives

2(1H)-Pyrazinone, which is in equilibrium with 2-pyrazinol, reacts with ben zonitrile oxide (BNO) affording the N-1-adduct with a 67% yield, while 2-me thoxypyrazine gives two methoxypyrazinones (ca. 3%) and a biscycloadduct to gether with its degradation product, which derive from the two unisolable m onocycloadducts to the C=N-4 double bond. N-Methylpyrazinone gives only the degradation product (3.4%) of the initial monocycloadduct of BNO to C=N-4 doable bond.