Efficient Trapping of Ketone Enolates With Acrylate and β-Sulfonylacrylate Thioesters, β-Sulfonyl-, β-Sulfinyl- and β-Chloro-Vinyl Ketones; Facile Preparation of a Hydrindanone, cis-Dimethyloctalone, and Unsaturated 1,5-Dicarbonyl Compounds

Tandem conjugate addition-ring closure involving reaction of the lithium enolate arising from conjugate addition of lithiated (E)-but-2- enyldiphenylphosphine oxide to 2-methyl-cyclopent-2-enone with two moles of t-butylthioacrylate generates a hydrindanol, and, in the presence of copper(I), a lactone derived from the hydrindanol. β-Sulfonylacrylate phenyl and t-butyl thioesters, β-chlorovinyl, β- sulfonyl- and β-sulfinyl-vinyl ketones react with the foregoing enolate, and with the enolate generated through conjugate addition of a methylcuprate to 2-methylcyclohexenone to give unsaturated 1,5-dicarbonyl compounds. The β-chlorovinyl ketones in particular react rapidly and in high yield. 2-Methylcyclohexenone has thereby been converted into a cis-dimethyl octalone; the conversion illustrates the effectiveness of β-chlorovinyl methyl ketone in the Robinson annelation. Reactions of the lithium enolate and titanium enol of 2,6- dimethylcyclohexanone with the β-substituted enones to give the corresponding unsaturated 1,5-dicarbonyl compounds and other products are also recorded.