The first example of a (1R,2S,5R)-(-)-menthyl chiral auxiliary in intramolecular nitrilimine cycloadditions: synthesis of enantiopure pyrazolo [1,5-a] [4,1]benzoxazepines and pyrazolo[1,5-a][4,1]benzodiazepines

摘要

By using (1R,2S,5R)-(-)-menthyl as a chiral auxiliary, we have developed a synthesis of hydrazonoyl chlorides 2 and 8, treatment of which with silver carbonate promoted the in situ generation of the corresponding nitrilimines 3 and 9. The latter underwent intramolecular cycloaddition giving, respectively, enantiopure pyrazolo[1,5-a][4,1]benzoxazepines 4, 5 and pyrazolo[1,5-a][4,1]benzodiazepines 10.