Abstract
Smooth conversion of telomers of vinylene carbonate with carbon tetrachloride or methylene bromide as a telogen to novel trans enol phosphates, and the reactivities of the phosphates thus formed are described. Both trans-"anti"-trans- and trans-"syn"-trans-isomers of the n=2 telomers, 5-chloro-5'-trichloromethyl-(4, 4'-bi-1, 3-dioxolan)-2, 2'-dione and 5-bromo-5'-dibromomethyl-(4, 4'-bi-1, 3-dioxolan)-2, 2'-dione gave, on treatment with trialkyl phosphites, the identical trans dialkyl 2-(5-trichloromethyl- and 2-(5-dibromomethyl-2-oxo-1, 3-dioxolan-4-yl) vinyl phosphates in good yields, without any detectable amount of cis isomer and the phosphonate, while the n=1 adduct failed to give the corresponding enol phosphate. Stereospecific conversion of the phosphate to cis 2-(5-trichloromethyl-2-oxo-1, 3-dioxolan-4-yl) vinyl acetate was readily achieved by new vinylic exchange reaction catalyzed by palladium chloride in acetic acid by way of the processes, trans oxypalladation and trans deoxypalladation. Reactions involving catalytic hydrogenation, chlorination with titanium chloride and conversion to α, β-unsaturated aldehydes are summarized in Chart 2.
