Reactions in Which the Coordinated Triple Bond Is Unaffected

Reactions in Which the Coordinated Triple Bond Is Unaffected 

An extension of the use of metal complexes to stabilize reactive intermediates is their utilization to deactivate reactive functional groups and hence to serve as protective groups. The propensity of transition metals to form stable complexes with olefins and acetylenes renders them particularly well suited to serve as protecting groups for carbon-carbon unsaturation. 

The dicobalt hexacarbonyl unit has been found to fulfill the three essential criteria of a protecting group for the carbon-carbon triple bond, namely (1) ease of introduction and removal (2) stability under conditions which effect 

The coordinated alkyne linkage in these species has been found to be relatively unreactive towards electrophilic reagents which attack the free triple bond. Whereas Friedel-Crafts acylation of arylacetylenes is complicated by attack at the triple bond, Seyferth and co-workers have shown that the corresponding cobalt complexes undergo selective acylation on the aromatic ring (Seyferth and Wehman, 1970 Seyferth et al, 1975c). Representative examples are shown. 

KENNETH M. NICHOLAS, MARA O. NESTLE, AND DIETMAR SEYFERTH 

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