摘要:
Results from the thermal reactions of deuterated dienes 12-15 provide evidence of the concertedness of the [4 + l]-cycloaddition between dimethoxycarbene and electron-deficient dienes. Other evidence suggests that the main pathway is a concerted [4 + 11]-cycloaddition rather than a cyclopropanation followed by a vinylcyclopropane rearrangement. Ionic pathways can become competitive when steric or geometrical constraints are present.