Silylketenes trimethylsilylketene

Since metal ynolates are metallated ketene equivalents, metallation of ketenes is expected to afford metal ynolates. Direct metallation of monoalkylketenes is, however, fairly difficult due to the high lability of these ketenes (e.g. dimerization) and the strong elec-trophilicity of the carbonyl carbon . In contrast, silylketenes are so stable that lithiation of trimethylsilylketene (45) with BuLi at —100 °C provides the lithium ynolate 46 in good yield (equation 18). The f-butyldimethylsilylketene (47) is also lithiated to afford the lithium ynolate 48 (equation 19). ... 

Trimethylsilylketene reacts similarly with carbonyl isocyanates to give [4+2] cycloadducts, which undergo a Diels-Alder reaction with acetylenes or enamines to give 2-pyridones. A theoretical study of the reaction of silylketenes with carbonyl isocyanates and subsequent Diels-Alder reaction with ynamines was conducted recently. ... 

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