Convergent Synthesis of Macrocycles Composed of 5-Amino-2H-1,2,4-thiadiazolin-3-one or 5-Amino-2H-1,2,4-thiadiazoline-3-thione and 1,3-Benzenedimethanethiol

Transition metal complexes with peripheral sites capable of hydrogen-bonding or π-stacking interactions to form groups have recently been used as hosts to bind neutral guests, such as aliphatic amines, aromatic amines, hydrazines, DNA nucleobases, amino acids, and barbiturate. This form of host is referred to as a metalloreceptor. The construction of hosts with metal ions in the scaffold has allowed the binding of many structurally sophisticated guests. Consequently, the design and study of various metalcontaining macrocycles is one of the most active and interesting areas in modern supramolecular chemistry. Coordinate covalent bond formation offers new prospects for selective molecular recognition, anion transport, and catalytic activation of electron-rich organic and inorganic substrates. It has long been recognized that multiple complementary interactions between the host and guest are of vital importance in stabilizing host-guest complexes (e.g., the chelation effect). Investigations of host-guest interactions and inclusion phenomena as well as biomimetic studies have become interesting targets. To obtain stable, reversible adducts, there is still a clear need for neutral molecular receptors that are simple and versatile, while they are also selective. This recalls the first stages of enzymatic processes, which involve the formation of a metallo-enzyme-substrate complex. We sought to prepare macrocycles composed of 5-membered cytosine analogues and 1,3-benzenedimethanethiol.