CLATHRATE FORMATION FROM 3-(2',2'-DIHALOVINYL)-2,2-DIMETHYLCYCLOPROPANECARBOXYLIC ACID AND AROMATIC-COMPOUNDS - PREPARATION, STRUCTURE, AND APPLICATION IN SEPARATION OF STEREOISOMERS

Clathrate formation was discovered and investigated in a series of stereoisomers of 3-(2',2'-dihalovinyl)-2,2-dimethylcyclopropanecarboxylic acid, 1 (X = Cl, Br). It was found that the equimolar mixture of (1R)-cis and (1S)-cis acids gives rise to crystalline inclusion complexes with simple aromatic compounds such as benzene, fluorobenzene, thiophene, pyrrole, furan, and 2-methylfuran, always in the stoichiometric ratio 1:1:1 with respect to the participating components. No other stereoisomeric mixture of any single enantiomer of the acid 1 forms inclusion complexes. The crystal structure of the inclusion complex obtained from the racemic cis acid 1 (X = Cl) and benzene was determined and compared with that of the neat racemic cis acid. Applicability of the novel inclusion complexes for separation of geometrical (cis vs trans) as well as optical ((1R)-cis or (1S)-cis vs (1RS)-cis) isomers has been demonstrated.