Dibromohydantoins as halogen bond (XB) donors: a route toward the introduction of chirality in halogen bonded systems?

CrystEngComm Pub Date: 2016-11-07 DOI: 10.1039/C6CE02175A

Abstract

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–CO2Me > Py–CF3 > 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.

Graphical abstract: Dibromohydantoins as halogen bond (XB) donors: a route toward the introduction of chirality in halogen bonded systems
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