Selective Intermolecular Photo-[4 + 4]-cycloaddition with 2-Pyridone Mixtures. 2. Preparation of (1α,2β,5β,6α)-3-Butyl- 9-methoxy-3,7-diazatricyclo[4.2.2.2^2,5]dodeca-9,11-diene-4,8-dione

Abstract

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