Pure and Applied Chemistry

Abstract: A variety of α,β-unsaturated acetylenic ketones, prepared in good yields from 3,3,4,4-tetraethoxybut-1-yne (TEB), have been reacted with selected mono- and bis-nucleophilic reagents. The mononucleophiles react in a Michael fashion and give in most cases the corresponding α,β-unsaturated alkenones in good yield. Many of the alkenes are formed as single stereoisomers, but the configuration depends on the nature of the nucleophile. If hydrogen bonds can be formed, the Z geometry is preferred, otherwise the E geometry is completely predominant. Experiments have also uncovered that α,β-unsaturated acetylenic ketones with a gem-diethoxy moiety in the α' position decompose when reacted with sodium hydroxide in aqueous tetrahydrofuran (THF); the carbonyl group is attacked and a carboxylic acid and a terminal alkyne are formed. If the nucleophiles contain two nucleophilic centers or if the α,β-unsaturated acetylenic ketones contain an additional reactive group, such as a hydroxyl group or an acyloxy moiety, useful secondary reactions may occur. By taking advantage of such secondary transformations, two completely regioselective syntheses of furans have so far been developed.