N-Methylated Diphenylguanidines: Conformations, Propeller-Type Molecular Chirality, and Construction of Water-Soluble Oligomers with Multilayered Aromatic Structures
文摘
The crystal structures ofN,N'-diphenylguanidine (1) and itsN-methylated derivatives wereinvestigated, and the conformational properties of these molecules wereutilized to construct water-solubleoligomers with multilayered aromatic structures.N,N'-Diphenylguanidine (1) afforded twotypes of crystals,chiral (P212121) andracemic (P21/c), uponrecrystallization from EtOH. In both crystals, 1 existsin the (E,Z)conformation, in which one C-N bond (length: 1.28-1.30 Å)attached to a phenyl ring shows double-bondcharacter. In contrast,N,N'-dimethyl-N,N'-diphenylguanidine(4a) exists in the (Z,Z) conformationwith thetwo aromatic rings facing each other. As judged from the crystalstructures of several N-methylated compounds,the conformational preferences of diphenylguanidines appear to berelated to those of aromatic anilides.N,N,N',N''-Tetramethyl-N',N''-diphenylguanidiniumiodide (6) afforded chiral crystals, like 1 andN-methyl-N,N'-diphenylguanidine (2). The absolutestructure of each enantiomeric propeller conformation of 6wasdetermined by X-ray analysis using the Bijvoet difference method.The Z-conformational preference of4allowed us to synthesize oligomeric di- or tetraguanidines(9-12) which have multilayered aromaticstructuresboth as a crystal and in organic and aqueous solvents.