Copper(II) Acetylacetonate: An Inexpensive Multifunctional Catalyst

Introduction

Copper(II) acetylacetonate [Cu(acac)₂] (Figure 1) is a ­soluble copper catalyst that has been widely employed in many types of reactions. It can be readily and easily prepared [1] from the reaction of acetylacetone with ­copper(II) sulfate in aqueous basic solution, and is ­isolated as a blue solid.

Figure 1 Copper(II) acetylacetonate

Although Cu(acac)₂ has been mostly used as catalyst in different reactions involving diazocompounds, [2] it is also described as a catalyst for other types of reactions such as benzylation of alcohols, [3] reduction of aromatic nitro ­compounds, [4] aziridination, [5] [6] and epoxidation. [6] The easy access and low cost of copper(II) acetylacetonate, to­gether with its varied applications as catalyst, make Cu(acac)₂ a powerful reagent in organic synthesis.

References

• Preparation of Cu(acac)₂: Copper(II) acetylacetonate was prepared by reaction of CuSO₄ with equimolar quantities of acetylacetone and NaOH in aqueous solution. After the subsequent addition of acetylacetone (1 equiv) and CuSO₄·H₂O (0.5 equiv) in basic solution with stirring, a blue precipitate was obtained. The precipitate was filtered, dried in vacuum and recrystallized from glacial AcOH to give blue needles:
• 1a Graddon DP. J. Inorg. Nucl. Chem.  1960,  14:  161 
• 1b For another experimental procedure, see: Peacock RD. J. Chem. Educ.   1971.  48:  p.133 
• 2For many applications of Cu(acac)₂ in reactions with diazo compounds, see:
• 2 Doyle MP. McKervey MA. Ye T. Modern Catalytic Methods for Organic Synthesis with Diazo Compounds From Cyclopropanes to Ylides   Wiley; New York: 1998. 
• 3 Sirkecioglu O. Karliga B. Talinli N. Tetrahedron Lett.  2003,  44:  8483 
• 4 Hanaya K. Muramatsu T. Kudo H. J. Chem. Soc., Perkin Trans. 1  1979,  2409 
• 5 Kantam ML. Kavita VNB. Haritha Y. Synlett  2004,  525 
• 6 Aggarwal VK. Synlett  1998,  329 
• 7 Burtoloso ACB. Correia CRD. Tetrahedron Lett.  2004,  45:  3355 
• 8 Solomon RG. Kochi JK. J. Am. Chem. Soc.  1973,  95:  3300 
• 9 Hudlicky T. Kutchan TM. Wilson SR. Mao DT. J. Am. Chem. Soc.  1980,  102:  6353 
• 10 Tan Z. Qu Z. Chen B. Wang J. Tetrahedron  2000,  56:  7457 
• 11 Hoshi M. Shirakawa K. Synlett  2002,  1101