Halogen bonding in Wagner-Meerwein rearrangement products

Reaction of (3aRS,6SR,7aRS)-6-substituted 2-phenyl-2,3,7,7a-tetrahydro-3a,6-epoxyisoindol-1(6H)-ones (1–3) with ICl (or Br2) in CH2Cl2 yields to halogenated Wagner-Meerwein rearrangement products, 4,5- (or 4,5,6)-halo-2-phenyloctahydro-4,6-epoxycyclopenta[c]pyridin-1-ones, with moderate yields (40–43%) of 4–6. All these polyhalogenated compounds are formed exclusively in the syn diastereomeric form relatively to halogen atoms at 4 and 5 positions of molecule. In 4–6 the halogenated carbon atoms exist as the S-stereogenic centers. The Cl ⋯ Cl and Cl ⋯ I types of halogen binding were found in the structures of 5 and 6, respectively, whereas molecules of 4 are stabilized in crystal by multiple hydrogen bonding. © 2017