Synthesis and characterization of chiral guanidines und guanidinium salts derived from 1-phenylethylamine

Abstract

The synthesis of two new chiral guanidines 5 and 12 and derived guanidinium salts 6, 11, 13 -15 with one and three N-(1-phenylethyl) substituents is described. In both cases, the well-precedented, reliable route via chloro-formamidines was taken. Since direct attachment of the N-methyl-N-(1-phenethyl)-amino group failed, the two-step protocol - introduction of the primary 1-phenethylamino group first followed by N-methylation - was employed. Crystal structures and NMR data reveal, that the sterically highly congested "tris" salt - with formal C3 symmetry, albeit unsymmetrical in the crystal - constitutes an intriguing structure with two rotamers present in solution. © 2012 Verlag der Zeitschrift für Naturforschung.