Six-Membered Rings With Two or More Heteroatoms With at Least One Selenium or Tellurium

This chapter comprises relevant aspects related to six-membered heterocycles containing 2–4 heteroatoms, among which at least one is a heavy chalcogen (selenium or tellurium) and covers the literature in the field published mainly during last 10 years. The compounds are discussed in separate chapters according to the number of heteroatoms in the six-membered ring and, further, in sub-chapters dedicated to isolate heterocycles, spiro derivatives and fused polycyclic systems. Further classification inside each sub-chapter takes into account the type of the additional heteroatom(s) in group 3–6 of the Periodic Table and the degree of saturation. Besides the reported data related to the synthesis procedures, relevant aspects related to the solution behavior and the solid state structure obtained by NMR spectroscopy and single-crystal X-ray diffraction, as well as data obtained by theoretical calculations for selected compounds are also discussed. Finally, the importance of selenium- and tellurium containing six-membered heterocycles for biology, medicine and optoelectronics is pointed out.