Synthesis of Base-Stabilized Silacyclohexadienones

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. 

The NHC-stabilized silacyclopentadienylidene Ph4C4)Si(hPr) was synthesized according to published procedures (7). 

Schlenk flask, magnetic stirrer, vacuum pump, low-temperature reactor, constant pressure funnel, safety glasses, laboratory coat, and protective gloves. 

NHC-stabilized silole silylene is air-sensitive. The synthetic experiments were carried out under an atmosphere of dry argon or nitrogen by using modified Schlenk line and glovebox techniques. All solvents were freshly distilled from Na and degassed immediately prior to use. 

The reaction products represent the first examples of silicon analogs of the ubiquitous enone and dienone compounds, which are potentially useful for the synthesis of novel unsaturated silicon—carbon heterocycles. 

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