Macrocyclic Polylactams of Mirror Symmetry: Preparation and Structure

The synthesis and structure of a series of macrocyclic lactams possessing reflection symmetry are described. The synthesis involves condensation of diazasilolidines 1 and 2 with diacyl dihalides 3 to give either exclusively macrocyclic dilactams 4 or tetralactams 5. The high product selectivity of these reactions is attributed to noncovalent interactions between silicon and carbonyl oxygen. The structures of the macrocyclic lactams prepared are analyzed by high-resolution ¹H and ¹³C NMR spectrometry as well as by X-ray diffraction studies. The observed conformational regularities are discussed and compared with those of macrocyclic lactams of rotational symmetry.