Intramolecular [4+2] Cycloaddition of ortho-Quinone Methides Generated In Situ
Catalytic Asymmetric Intramolecular [4+2] Cycloaddition of In Situ Generated ortho-Quinone Methides.
Angew. Chem. Int. Ed. 2017;
18 April 2017 (online)
Key wordsconfined chiral acids - furanochromanes - quinone methides - cycloaddition - asymmetric catalysis
The List group has developed a catalytic, asymmetric, intramolecular [4+2] cycloaddition of in situ generated ortho-quinone methide. A variety of salicylaldehydes were treated with dienols in the presence of a confined, chiral imidodiphosphoric acid catalyst to provide the desired furanochromanes with excellent enantioselectivities and good yields.
The chromane moiety is frequently found in natural products. The obtained furanochromane products have highly functionalized tricyclic frameworks. This acid-catalyzed reaction may be suitable for natural product synthesis, as two rings and three consecutive stereocenters are formed in a single step.