Silylene-dicarbenes

To date, bis(diazomethyl)silanes represent the only precursors to silylene-dicarbenes. It should be noted, however, that the extrusion of N2 from the two diazo functions can occur more or less simultaneously or successively. In the latter case, a diazocarbene is formed in the first place, which is supposed to undergo a fast carbene reaction before the generation of a carbene from the second diazo function occurs. This should be kept in mind for all transformations which are explained mechanistically with the participation of silylene-dicarbenes. There are even examples where only one of the two diazo groups enters carbene chemistry at all (see equations 35 and 36 below). 

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