Thiourea compounds, thiocarbonyl ylide

As mentioned earlier, the first example of the generation of a thiocarbonyl ylide by deprotonation of a thioxonium salt was reported by Knott (18) and is presented in Scheme 5.1. This method is frequently used since the starting materials 32 are easily available via alkylation of C=S functionalized compounds such as thioke-tones, thioamides, thiourea derivatives, and dithioesters (Scheme 5.11). 

Typically, thioxonium salts (32) are stable compounds, and the deprotonation is performed at low temperatures. This method has been used to synthesize reactive thiocarbonyl yhdes as well as stable and isolable ones (56-60). Arduengo and Burgess (3) prepared differently substituted thiocarbonyl ylides from thiourea derivatives, and in the case of 33, the structure has been established by X-ray crystallography. 

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