Endo-selective Diels–Alder reaction of methacrylonitrile: application to the synthesis of Georgywood

Diels–Alder reactions of alkyl-substituted dienes with acrylonitriles give good yields and endo-selectivities if catalyzed by (organo)aluminum, (organo)boron or gallium halides. The activity of these group IIIa Lewis acids in this reaction correlates with the coordination strength of their nitrile complexes, which deactivate Lewis acids sufficiently, so that the subsequently added diene partner undergoes the Diels–Alder reaction without serious side-reactions. Boron trichloride is the most effective catalyst for this purpose. This method gives the best endo/exo-ratios reported so far for these components and was applied in the selective synthesis of the olfactory vector of Georgywood®.