Palladium catalyzed transfer vinylation of simple alcohols and protected monosaccharides
4,7-Diphenyl-1,10-phenanthrohne bis(trifluoroacetato) palladium(II) is an effective catalyst for the transfer vinylation of simple alcohols and protected monosaccharides using simple commercially available alkyl vinyl ethers as the vinyl source. The transfer vinylation reaction was initially optimized with simple alcohols since the products could be quickly and easily identified by gas chromatography. Subsequently much more complicated monosaccharide structures were successfully vinylated and structurally characterized. An analysis of the time to equilibrium and yield of the vinyl ethers obtained from simple alcohols revealed that the yield decreased in order of primary, secondary and tertiary alcohols and that steric bulk on either vinyl ether or alcohol is tolerated, but not on both. Only vinyl ethers with hydrogen on the [alpha]-carbon of the vinyl group can serve as the vinyl source. That is, the method is limited to unsubstituted ethenyl ethers. In cyclic six membered alcohols the alcohol group in the equatorial position reacts faster than that in the axial orientation. The palladium catalyst also efficiently catalyzed the transfer vinylation between 'n'-butyl vinyl ether and various allyl alcohols to give the corresponding allyl vinyl ethers as the first direct catalytic route for this class of compounds. Transfer vinylations of protected monosaccharides yield primary and secondary sugar vinyl ether in moderate to good yield. Protected monosaccharides with two alcohol groups available for vinylation, afforded a mixed divinyl, and two monovinyl products with low to moderate yields providing interesting synthons for further use. A protected monosaccharide with three alcohol groups available for vinylation also afforded a mix of different vinyl products, some of which are of synthetic use.