Silicon-carbon compounds silols

Compounds containing the silicon-carbon double bond have been prepared (Scheme 85) and derivatives of silabenzene and germabenzene have been characterized (Section 1.20.13). Methyllithium and n -butyllithium will alkylate the silole (126) showing the ring silicon to be the site for nucleophilic attack. The reaction is quantitative and no silole anion (127) was detected (Scheme 205) (8lJOM(2l8)C2l). 

The reaction of silole 44 with KH in THF or DME yields, after work-up with D2O, quantitatively the corresponding deuteriated silole (equation 52) metalated siloles have been suggested as intermediates80. In contrast, the analogous treatment of silole 45 with KH yields a mixture of three NMR spectroscopically characterized potassium compounds (equation 53). The main product of this reaction is the pentavalent silicate 46, which results from the nucleophilic attack of a hydride at the silicon center109. The other two products result from hydride addition to one of the ring carbons. 

Reactions of silylenes with unsaturated organic substrates are valuable for the synthesis of novel silicon compounds (1,2). Over the past three decades, the reactions of silylenes with carbonyl compounds have been extensively investigated (3—5). It has been shown that these reactions produce diverse types of products via siloxirane or carbonyl silaylide intermediates while the carbonyl C—O a bond is generally maintained (3—5). Complete cleavage of the C—O bond has only been observed in several cases (4). Furthermore, the synthesis and physical properties of siloles and related unsaturated carbon—silicon heterocycles are of great interest as heteroaromatic molecular precursors and potential molecular optical materials (6). In this experiment, reaction of a NHC-stabilized silacyclopentadienylidene (silole silylene) with aldehydes, leading to the formation of the novel NHC-stabilized a,(3-unsaturated silanone, was described. 

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