Conversion of methoxy vinyl ethers into glyoxal ketals
Dilzer, Kirsten France
Ciufolini, Marco A.
Master of Arts
A technique for the elaboration of ene products derived from aldehydes and 2-methoxypropene into glyoxal monoketals 5 has been devised, and some reactions of the resulting aldehydes have been examined. This methodology should resolve some difficulties encountered in the course of an ongoing total synthesis of phyllanthocin. Key phases of the present study involve oxidation of ether 1, readily available from butyraldehyde through a novel ene-type reaction discovered in our laboratory, using mCPBA and methanol to give a cyclic ketal 2. The resulting seven-membered ring was opened by ketal exchange with 1,3-propanethiol to give thioketal diol 3. Benzylation of the diol proceeded with complete selectivity for the primary alcohol, permitting differentiation of the diol functionality. Protection of the secondary alcohol as a MOM derivative and subsequent ketal exchange with bis(trifluoroacetoxy)iodobenzene reinstated the dimethoxy ketal. Debenzylation under Birch conditions released the free primary alcohol 4, Swern oxidation of which yielded the desired aldehyde 5.* ftn*Please refer to the dissertation for diagrams.