Silicon heterocycles, four-membered

Figure 1 Silicon-containing five-membered heterocycles with three or four heteroatoms.

In the chemistry of silicon, heterocycles are rings containing silicon atoms and one or more of another type of atom. Of the isocyclic compounds, four to seven-membered rings are known, while the existence of an eight-membered ring is probable. The same or similar ring sizes are expected for heterocyclic silicon compounds. 

A series of four-membered Si- or P-containing heterocycles was produced in various yields by electrocyclization or [2-t-2]-dimerization of compounds with multiple carbon-silicon or carbon-phosphorus bonds. These unsaturated species are formed under photolysis of diazo compounds containing a P or Si atom in an a position with respect to the diazo group, following a [l,2]-sigmatropic shift in the intermediate carbene. 

Four-membered silicon heterocycles, formation and properties of 79CRV529. 

Four-membered heterocyclic systems have been postulated to be involved as intermediates along the reaction pathway in a number of systems allowing olefin synthesis. This is the case of the Wittig reaction (phosphorus) and a family of related reactions the boron-Wittig (boron), the Peterson (silicon) 44 and the Peterson-type reactions (germanium, tin, lead). 5,l46 11 these systems,... 

The study of the chemistry and biology of strained four-membered heterocycles has become an extremely active field of research in 2014. In this chapter, the reader will find a brief discussion of new contributions focused on fields such as organic synthesis and medicinal chemistry. For the sake of clarity, contributions are separated in sections depending on the nature of the heteroatom. Although oxa- and azaheterocycle derivatives dominate the field in terms of the number of scientific pubheations, the chemistry of sulfur-, silicon-, and phosphorus-based heterocycles is also of great relevance.The aim here is not to provide an in-depth analysis of all the vast scientific Hterature concerning four-membered heterocycles during the calendar year 2014. Consequently, there are many examples that are cited but not covered in detail. 

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