Reaction of ketones or aldehydes with 1-alkynes over solid-base catalysts Original Research Article

Various strong solid-bases catalyzed the reactions of 1-alkynes with ketones to synthesize 1-alkynyl alcohols. For example, the reaction of phenylacetylene with cyclohexanone in the presence of KNH2 loaded on Al2O3 (KNH2/Al2O3) gave 1-(phenylethynyl)cyclohexan-1-ol 10 in a 87% yield at 363 K in 20 h. Strong solid-bases also catalyzed the reactions of aldehydes with 1-alkynes, the main products being α,β-unsaturated ketones, but not alkynyl alcohols. Thus, Cs2CO3/Al2O3 gave mainly 1,3-diphenyl-2-propen-1-one (chalcone) 8 from phenylacetylene with benzaldehyde. The reaction offers a new route for the synthesis of chalcones. The reaction mechanism for the formation of 8 was discussed based on the reaction using deuterated benzaldehyde, PhCDO. It was also found that 1,3-diphenylprop-2-yn-1-ol 19 was easily isomerized to 8 in the presence of Cs2CO3/Al2O3. This is the first example of a rearrangement of 1-alkynyl alcohol to an α,β-unsaturated ketone.