Copper-catalyzed synthesis of 1,3,5-triarylpentane-1,5-diones from α,β-unsaturated ketones

Abstract

An efficient method for copper catalyzed synthesis of 1,3,5-triarylpentane-1,5-diones using a,bunsaturated ketones as unique starting materials is described. The protocol offers several advantages such as simple, inexpensive reagents, mild reaction conditions and simple work-up procedure.

One-Pot Synthesis of 1,5-Diketones under a Transition-Metal-Free Condition: Application in the Synthesis of 2,4,6-Triaryl Pyridine Derivatives

“…Accordingly, 2 equiv of compound 1a were dissolved in anhydrous ethanol in the presence of 1 equiv of aqueous KOH and the reaction mixture was stirred for 0.25 h at 0 °C. After the enol formation was ensured, 1 equiv of benzaldehyde ( 2a ) was added and the reaction temperature was raised to room temperature (rt) to afford the well-known 1,5-diketone 3a at a yield of 37% over 18 h (Table , entry 1). The yield of 1,5-dione 3a was slightly improved to 40% upon employing 2 equiv of KOH under the same temperature and reaction time (Table , entry 2); however, the yield declined to 36% with a shorter reaction time (Table , entry 3).…”

“…Consequently, much effort has been devoted to the chemical synthesis of 1,5-diketones. ,, The most common classical methods of 1,5-diones synthesis are (i) Claisen–Schmidt condensation following Michael addition reaction of aryl methyl ketones and benzaldehyde derivatives under a basic condition − and using silica vanadic acid as a heterogeneous catalyst (Scheme a), (ii) catalyzed Michael reactions of chalcones (α,β-unsaturated ketones) with aryl methyl ketones, silyl enol ethers, , and diphenacyl sulfides (Scheme b), (iii) from α,β-unsaturated ketones via base-induced retro-aldol and Michael addition using copper and cobalt as catalysts, , (Scheme c), (iv) via nickel on silica-alumina-catalyzed direct α-alkylation of aryl methyl ketones with benzyl alcohol (Scheme d), and (v) silver- and rhodium-catalyzed reactions of aromatic and aliphatic aldehydes with cyclopropanol and cyclobutanol derivatives. , However, these synthetic methods use expensive catalysts and additives, toxic organic solvents, and air- and moisture-sensitive materials. Additionally, the yields of 1,5-diketones through these reactions were low either due to by-product formation such as aromatic aldehydes , or no product formation at all under base-mediated condensation . Hence, the search for an efficient synthetic method for 1,5-diketones based on inexpensive starting materials should be given high attention in organic chemistry.…”

“…1,34 However, these synthetic methods use expensive catalysts and additives, toxic organic solvents, and air-and moisture-sensitive materials. Additionally, the yields of 1,5diketones through these reactions were low either due to byproduct formation such as aromatic aldehydes 31,32 or no product formation at all under base-mediated condensation. 22 Hence, the search for an efficient synthetic method for 1,5-diketones based on inexpensive starting materials should be given high attention in organic chemistry.…”