Cyclotrisilanes synthesis

In view of the extensive chemistry of alkenes it wus only natural for organic and inorganic chemists to search for analogous Si=Si doubly bonded structures. For a long time such attempts proved to be fruitless. The first stable C—SiB and Si=Si9 compounds were synthesized about a decade ago. One synthesis involves the rearrangement of cyclotrisilane ... 

Functionalized cyclotrisilane derivatives bearing oxygen- or nitrogen-containing substituents are also known. The synthesis of the aryl-alkoxy cyclotrisilane trimesityl-tris(2,6-diisopropylphenoxy)cyclotrisilane can be easily accomplished by the photolysis of 2-mesityl-2-(2,6-diisopropylphenoxy)-l,l,l,3,3,3-hexamethyltrisilane via several silylene extrusion and addition steps (equation 7)40. 

Recently, ultrasound has been very successfully applied to different organ-ometallic and catalytic reactions (15). Rates are strongly accelerated, and reactions are often much more selective than those carried out under typical thermal conditions. Sonication of sterically hindered dichlorosilanes in the presence of lithium yields disilenes and cyclotrisilanes 16, 17). We have applied ultrasound in the synthesis of poly(phenylmethylsilylene) in the presence of dispersed sodium, which was prepared directly from small pieces of sodium by sonication. 

Also covered is the stabilisation of Ge, Sn, and Pb carbanion equivalents, carbene analogues, cyclotrisilanes and tristannanes. Main Group organometallics in synthesis, applications of Si and Sn in borane chemistry and cross-coupling, disilenes and... 

The transition-metal-catalyzed [2 + 2 + 1] cycloaddition of two alkynes and heteroatom sources is a useful method for the synthesis of five-membered heterocycles. For example, a silylene species reacts with two alkynes 64 in the presence of nickel or palladium catalyst to afford substituted siloles 65 and 66. Various silylene equivalents, such as disilanes 67 [24], silacyclopropenes 68 [25], 69 [26], cyclotrisilanes 70 [27], alkylidenesilacyclopropanes 71 [28], silacyclopropanes 72, and 73 [29], have been developed as shown in Scheme 6.21. However, the utility for organic synthesis has been limited, due to the difficulty of those organosilane syntheses and the narrow alkyne scope. 

Similar to the chemistry of cyclotrisilanes also for that of the respective fonr-membered rings initially mainly the Wurtz-type coupling protocol was used as the synthetic approach. For the synthesis of cycloalkyl substituted cyclotetrasilanes Roewer and coworkers were employing this strategy (4) [97]. 

As already shown above for cyclotrisilanes, ohgosilanyl dianions are convenient building blocks for the synthesis of cyclosilanes with different substitution pattern [47, 96, 108]. l,l,2,2-Tetrakis(trimethylsilyl)tetramethylcyclotetrasilane which forms in the oxidative coupling of the 1,4-dipotassium compound (Scheme 8) can... 

Masamune S, Hanzawa Y, Murakami S, Bally T, Blount JF (1982) Cyclotrisilane (R2Si)3 and disilene (R2Si SiR2) system synthesis and characterization. J Am Chem Soc 104 1150... 

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