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

Various strong solid-bases catalyzed the reactions of 1-alkynes with ketone s to synthesize 1-alkynyl alcohols. For example, the reaction of phenylacet ylene with cyclohexanone in the presence of KNH2 loaded on Al2O3 (KNH2/Al2O 3) 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-alkyn es, the main products being alpha,beta-unsaturated ketones, but not alkynyl alcohols. Thus, Cs2CO3/Al2O3 gave mainly 1,3-diphenyl-2-propen-1-one (chal cone) 8 from phenylacetylene with benzaldehyde, The reaction offers a new r oute for the synthesis of chalcones. The reaction mechanism for the formati on 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 isom erized to 8 in the presence of Cs2CO3/Al2O3. This is the first example of a rearrangement of 1-alkynyl alcohol to an alpha,beta-unsaturaled ketone. (C ) 2000 Elsevier Science B.V. All rights reserved.