Diazoalkanes dediazotation reaction

The dediazotation reaction of various diazoalkanes (reaction 8.34) was successfully applied in the preparation of stable dinuclear cobalt carbene complexes (16) containing Tj -cydopentadienyl ligands [66-71]. 

According to theoretical calculations, there is a low-energy pathway for the direct interaction of diazomethane with carbon monoxide [4j. However, experimental results so far show only evidences for two-step pathways. These involve first the dediazotation of the diazoalkanes in thermal, photochemical, or transition metal mediated reactions [5] resulting in free carbenes (Equation 8.2) or transition metal coordinated carbenes (Equation 8.3), which under proper reaction conditions couple in the second step with carbon monoxide (Equation 8.4 or 8.5) to form ketene products. 

Scheme 8.1 Catalytic dediazotation of diazoalkanes and accompanying reactions with electron-rich reagents.

Manganese carbonyl complexes LMn(CO)2(THF) (L=ti -CH3C5H4 or ti -CsHs) were found to be effective in the dediazotation of diazoalkanes and in the formation of stable manganese carbene carbonyl complexes. See for examples reactions 8.23 and 8.24 [47,48]. 

Despite the fragmentary results known to date, the dediazotation of diazoalkanes coupled with the carbene-carbon monoxide trapping reaction seems to be a promising synthetic path for the preparation of various carboxylic acid derivatives through the ketene intermediate product. Especially the highly effective and selective cobalt-catalyzed examples of the reactions are worth to explore in more detail. 

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See also in sourсe #XX -- [ ]

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