Dibromohydantoins as halogen bond (XB) donors: a route toward the introduction of chirality in halogen bonded systemsCCDC 1509929-1509933. For crystallographic data in CIF or other electronic format see DOI: 10.1039/c6ce02175a

N , N′ -Dibromohydantoins, known as electrophilic bromination reagents, are successfully used here as halogen bond (XB) donors, as demonstrated in their crystalline adducts with para -substituted pyridines acting as halogen bond acceptors. 1 : 1 adducts of the achiral 5,5-dimethyl- N , N′ -dibromohydantoin (DBH) are crystallized with methylisonicotinate, 4-trifluoromethylpyridine and 4-cyanopyridine, while both nitrogen atoms of pyrazine are engaged in halogen bonding in the 2 : 1 adduct (DBH) 2 ·(pyrazine). A strengthening of the XB interaction between the imidic N-Br group of DBH and the pyridinic nitrogen atom is observed with the more electron rich pyridines in the order Py-CO 2 Me > Py-CF 3 > Py-CN > pyrazine. Chiral hydantoins and their N , N′ -dibromo derivatives are obtained in good yields from different amino acids (phenylglycine, phenylalanine, valine and leucine). The ability of such enantiopure N -iodoimide derivatives to act as halogen-bond donors is demonstrated in the 1 : 1 methylisonicotinate adduct with ( S )-5-isobutyl- N , N′ -dibromohydantoin. N , N′ -Dibromohydantoins, also prepared in chiral form, act as powerful halogen bond donors toward 4-substituted pyridines.