Selective intermolecular photo-[4+4]-cycloaddition with 2-pyridone mixtures. 2. Preparation of (1 alpha,2 beta,5 beta,6 alpha)-3-butyl-9-methoxy-3,7-diazatricyclo[ 4.2.2.2(2,5)]dodeca-9,11-diene-4,8-dione

Photochemistry of 2-pyridone mixtures can be selective and thereby lead to useful quantities of [4 + 4] cycloaddition cross products. The selective in termolecular reaction described here employs an excess of 4-methoxy-2-pyrid one (6), which does not photodimerize but will undergo [4 + 4] cycloadditio n with 2-pyridones without a 4-methoxy group such as N-butyl-2-pyridone 12. Isolated yields of the trans product ( 1 alpha,2 beta,5 beta,6 alpha)-3-bu tyl-9-methoxy-3,7-diazatricylo[4.2.2.22(2,5)]dodeca-9-11-diene-4,8-dione (7 ) are very sensitive to the ratio of the two starting pyridones, and this p roduct has been isolated in yields of up to 51%. This photoreaction produce s, in a single step from simple aromatic precursors, a tricyclic product wi th four stereogenic centers and four distinct functional groups.