Five-membered rings with two adjacent heteroatoms with at least one other element

Developments in the chemistry of five-membered ring heterocycles containing two adjacent heteroatoms, with at least one silicon or germanium, in the period 2008–20 are reviewed. Application of theoretical and structural methods to these compounds is described including X-ray structure determination and ²⁹Si NMR. The major reactions of azasiloline and oxasiloline systems as well as heavier chalcogen and benzo analogs are discussed. This is followed by a briefer discussion of azagermoline and oxagermoline reactivity. Methods for the synthesis of both silicon and germanium systems are systematically covered. The systems containing germanium have only been reported recently and were not included in previous editions of Comprehensive Heterocyclic Chemistry.