Carbenes alpha elimination

FRITSCH BUTTENBERG - WIECHELL Acetylene Synthesis Alpha elimination from haloethylenes leading via carbene rearrangement to acetylenes... 

The silicon analogue of carbene is now called silylene and it was discovered by the thermally-induced alpha elimination of methoxydisilanes. The most common method of silylene generation is ... 

The initial product of elimination is a highly electron-deficient species, usually a carbene or a nitrene, which subsequently reacts rapidly to give products. The base-catalysed hydrolysis of chloroform is an alpha-elimination . The properties of the electron-deficient species represent a rapidly expanding field of organic chemistry and this subject is discussed in the following chapter. In this chapter, only apparent alpha-eliminations, (e.g. reaction (5)), are included. The nature of the products indicates the intermediacy of electron-deficient species, but kinetic studies show the processes occur via reactions of the precursor carbanions, viz. 

The mechanism of the reaction (see Eq. 3.10) is believed to involve initial coordination of the electrophilic carbene to the nitrogen lone pair. The zwitterion thus formed undergoes proton transfer from nitrogen to carbon yielding an N-substituted aminodichloromethane. Base catalyzed beta-elimination of the elements of HQ followed by alpha-elimination of another mole of HCl yields the desired isonitrile. 

---