2-cyclohexenone 2-alken-l-one

Larock has developed an effective gold(III)-catalyzed method for the conversion of 2-(l-alkynyl)-2-alken-l-ones to substituted furans [28]. As an example, treatment of cyclohexenone 15 with methanol and a catalytic amount of AUCI3 in dichloromethane at room temperature for 1 h led to isolation of furan 16 in 88% yield (Eq. (12.10)). Liang has demonstrated the suitability of ionic liquids as solvents for this transformation [29]. 

Intermolecular de Mayo reactions are efficient for cyclic 1,3-diketones such as dimedone (5,5-dimethyl-l,3-cyclohexanedione)96,103,104 and acyclic systems such as acetylacetone93-95. Unsymmetrical acyclic /l-diketones, such as 1-phenyl-1,3-butanedione98 can enolize in two directions, however, reaction normally occurs preferentially from a single enol form. Examples of alkene photocycloaddition to trapped ends of /(-dicarbonyl compounds (e.g., 2,2-dimethyl-3(2/f)-furanone and 2,2.6-trimethyl-4/f-l,3-dioxin-4-one) are given in Table 1 (entries 26, 27) and Table 2 (entry 35) 10°. If the enol is stabilized by derivatization (e.g., acetylated dimedone 3-acetoxy-5,5-dimethyl-2-cyclohexenone), the primary cyclobutane photoproducts can be isolated96. 

Metallation of l-methoxy-2-butyne with n-butyllithium at -78 C, followed by the addition of one equivalent of zinc chloride, generates the very reactive and unisolable organozinc intermediate. Reaction of this zinc reagent with cyclohexenone affords the alkynic alcohol in 95% yield as a 65 35 mixture of diasteieomers. Subsequent reduction of the triple bond provides either the trans alkene or the cis alkene, depending on the reaction conditions. A modified oxy-Cope rearrangement thus provides the dia-steieomeric ketones, which have been used for the synthesis of juvabione (Scheme 29). ... 

The //4-0X0 cluster [Pd6Cu4Cli204(HMPA)4] catalyzes the oxidation of alkenes to ketones by 02. Oxidation of cyclohexene to a mixture of cyclohexanone and cyclohexenone (88 12) was achieved in 360% yield by use of the polymeric complex [ClCuL4(/i-Cl)PdCl2 PdCl2] (L = pyrrolidin-2-one) as catalyst. ... 

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