The Lewis Acidic Ruthenium-Complex-Catalyzed Addition of β-Diketones to Alcohols and Styrenes Is in Fact Brønsted Acid Catalyzed
✍ Scribed by Pei Nian Liu; Zhong Yuan Zhou; Chak Po Lau
- Publisher
- John Wiley and Sons
- Year
- 2007
- Tongue
- English
- Weight
- 403 KB
- Volume
- 13
- Category
- Article
- ISSN
- 0947-6539
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✦ Synopsis
Abstract
The perchlorate salt of the dicationic bipy–ruthenium complex cis‐[Ru(6,6′‐Cl~2~bipy)~2~(H~2~O)~2~]^2+^ effectively catalyzes addition of β‐diketones to secondary alcohols and styrenes to yield the α‐alkylated β‐diketones. In a catalytic addition reaction of acetylacetone to 1‐phenylethanol, the κ^2^‐acetylacetonate complex [Ru(6,6′‐Cl~2~bipy)~2~(κ^2^‐acac)]ClO~4~ was isolated after the catalysis; this complex is readily synthesized by reacting cis‐Ru(6,6′‐Cl~2~bipy)~2~(H~2~O)~2~~2~ with acetylacetone. [Ru(6,6′‐Cl~2~bipy)~2~(κ^2^‐acac)]ClO~4~ is unreactive toward 1‐phenylethanol in the presence of HClO~4~; it also fails to catalyze the addition of acetylacetone to 1‐phenylethanol. On the basis of these observations, it is proposed and confirmed by independent experiments that the catalytic addition of β‐diketones to the secondary alcohols is in fact catalyzed by the Brønsted acid HClO~4~, which is generated by the reaction of cis‐Ru(6,6′‐Cl~2~bipy)~2~(H~2~O)~2~~2~ with the β‐diketone.