Four-membered Rings with Three Heteroatoms with at least One Oxygen, Sulfur or Nitrogen Atom

Abstract

The progress in the synthesis, spectral characterization, reactivity, and other aspects of the comprehensive chemistry of the four-membered ring heterocycles with three heteroatoms and with at least one N, O, or S atom is reviewed for the period since 1995. The discussed synthesis methods cover the four-ring preparation from acyclic compounds using [2+2] and [3+1] cycloaddition, [3+1] and intramolecular cyclocondensation reactions, and transformation of various ring systems to four rings by ring insertion or contraction reactions. The preparation of four rings possessing heavier group 14 elements from intermediates kinetically stabilized by bulky ligands at the metal atom is described. The four rings main geometric parameters obtained by a single-crystal X-ray analysis are presented in tables. The data of 1H-, 13C-, 19F-, 29Si-, 31P-, 77Se-, 119Sn-NMR spectroscopy concerning the chemical shifts of the four-ring skeleton atoms are summarized. The reactivity of nonconjugated four rings, including ring cleavage, ring expansion, contraction, and rearrangement reactions, is described. Examples of quantum-chemical calculations applied to the theoretical investigation of the model compounds and reactions are presented. Finally, data on application of four-ring containing heterocycles as radioprotectors and antimicrobial agents are discussed.