Science of Synthesis

Austin, D. J.; Miller, S. M., Science of Synthesis, (2005) 21, 99.

Dicobalt octacarbonyl is a versatile transition-metal catalyst, which is particularly valuable in the widely used Pauson--Khand cyclization of alkene/alkyne substrates to form cyclopentenones. Derivatives of this catalyst can be formed under a variety conditions including phase-transfer catalysis. One such derivative is acetylcobalt tetracarbonyl, which finds use as an acetyl-transfer reagent for the formation of ketones and, analogously, for the formation of acetamides from imines. In a procedure of the latter type azadienes ‌53‌ can be reacted with acetyl(tetracarbonyl)cobalt to provide the corresponding allylic amides ‌56‌ in good yields.[‌44‌] The mechanism may involve the following steps: 1,2-addition of the acetylcobalt species, generated in situ, to the imine double bond provides the ­σ-allylcobalt complex ‌54‌, which is converted into a π-allyl complex ‌55‌ with loss of carbon monoxide and coordination of the amide oxygen atom to the metal. This complex is then hydrolyzed to the amide ‌56‌. A secondary reaction is acetylation of the amine component of the starting imine to form the corresponding acetamide ‌57‌; this becomes increasingly important as the temperature of the reaction increases (‌Scheme 29‌).[‌45‌]

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References

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• 8.Meeeee-Meee, (8888) M 8-8, 8888.