N-METHYLATED DIPHENYLGUANIDINES - CONFORMATIONS, PROPELLER-TYPE MOLECULAR CHIRALITY, AND CONSTRUCTION OF WATER-SOLUBLE OLIGOMERS WITH MULTILAYERED AROMATIC STRUCTURES

The crystal structures of N,N'-diphenylguanidine (1) and its N-methyla ted derivatives were investigated, and the conformational properties o f these molecules were utilized to construct water-soluble oligomers w ith multilayered aromatic structures. N,N'-Diphenylguanidine (1) affor ded two types of crystals, chiral (P2(1)2(1)2(1)) and racemic (P2(1)/c ), upon recrystallization from EtOH. In both crystals, 1 exists in the (E,Z) conformation, in which one C-N bond (length: 1.28-1.30 Angstrom ) attached to a phenyl ring shows double-bond character. In contrast, N,N'-dimethyl-N, N'-diphenylguanidine (4a) exists in the (Z,Z) conform ation with the two aromatic rings facing each other. As judged from th e crystal structures of several N-methylated compounds, the conformati onal preferences of diphenylguanidines appear to be related to those o f aromatic anilides. N,N,N',N ''-Tetramethyl-N',N ''-diphenylguanidini um iodide (6) afforded chiral crystals, like 1 and N-methyl-N,N'-diphe nylguanidine (2). The absolute structure of each enantiomeric propelle r conformation of 6 was determined by X-ray analysis using the Bijvoet difference method. The Z-conformational preference of 4 allowed us to synthesize oligomeric di- or tetraguanidines (9-12) which have multil ayered aromatic structures both as a crystal and in organic and aqueou s solvents.