Cyclic silaether

The concept of the generation of silylenium ion by hydride abstraction with a stable carbenium ion has been explored in designing the synthesis of saturated and unsaturated cyclic silaethers (104). For this purpose the incipient silylenium ion is intramolecularly trapped by a properly located ethereal nucleophile, which leads to cyclization [Eq. (21)]. If the triphenyl-... 

Cationic polymerization of cyclic silaethers, octamethyl-l,4-dioxa-2,3,5,6-tetrasilacyclohexane [Eq. (178)] and octamethyl-l-oxa-2,3,4,5-tet-rasilacyclopentane [Eq. (179)] was also reported [256] ... 

Cyclic monomers that have been polymerized via ring-opening encompass a variety of structures, such as alkanes, alkenes, compounds containing heteroatoms in the ring oxygen [ethers, acetals, esters (lactones, lactides, and carbonates), and anhydrides], sulfur (polysulfur, sulfides and polysulfides), nitrogen [amines, amides (lactames), imides, N-carboxyanhydrides and 1,3-oxaza derivatives], phosphorus (phosphates, phosphonates, phosphites, phosphines and phosphazenes), or silicon (siloxanes, silaethers, carbosilanes and silanes). For the majority of these monomers, convenient polymerization conditions have been elaborated, that result in the controlled synthesis of the corresponding polymers [1-13]. 

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