Evidence for the 1,4-Addition of Hydrogen Halides to α,β-Unsaturated Ketones. The Dibenzoylmonohalogenoethylenes

The Effect of Configuration of Certain Unsaturated 1,4-Diketones on Addition-Cyclization Reactivity

“…In this connection attention should be called to the remarkable case of one cis-trans pair, the dibenzoylchloroethylenes (I: R = Cl), where both of the two type reactions can be effected, furanization (4) and conversion to a furanone (5-7). In the addition of hydrogen chloride in 95% ethanol which gives the dichloro saturated diketone and the dichlorofuran, there is no evident distinction between the stereoisomers in respect to ratio and ease of addition-furanization (to II: R and Y = Cl); on the other hand both isomers are converted to the ethyoxyfuranone (IV: R = Cl, Y = OCzH6) when absolute ethanol is used as the solvent.…”