One-Pot Synthesis of 1,3,5-Tribenzoylbenzenes by Three Consecutive Michael A...

 

 

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One-Pot Synthesis of 1,3,5-Tribenzoylbenzenes by Three Consecutive Michael Addition Reactions of 1-Phenyl-2-propyn-1-ones in Pressurized Hot Water in the Absence of Added Catalysts

przez Chemistry – A European Journal autor: Toshihiko Hiaki dnia 10-11-12

Abstract

Cyclotrimerization of 1-phenyl-2-propyn-1-one in pressurized hot water gave 1,3,5-tribenzoylbenzene in one pot in 65 % yield after 7 min at 200 °C, or in 74 % yield after 60 min at 150 °C. The reaction did not take place in the absence of water, and added base promoted the reaction at 250 °C, suggesting a mechanism of three-consecutive Michael addition reactions. The reaction rates increased with temperature, but the yield of 1,3,5-tribenzoylbenzene decreased at the expense of formation of acetophenone as a side product at higher temperatures. p-Methyl and p-chloro-substituents on the phenyl ring retarded and enhanced the reaction, respectively. A mechanism involving the enol of benzoylacetaldehyde at a branching point of the pathway leading to 1,3,5-tribenzoylbenzene and acetophenone was suggested.

Under critical pressure! In sub- and supercritical water, the cyclotrimerization reaction shown in the scheme proceeds without any additive (X=ambient OH⁻) in a few minutes, and the solid product is obtained simply by filtration of the water after cooling.

 

 

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