A regioselective Tsuji-Trost reaction of sodium 3-allyl-tetronate
with methyl 5-trimethylsilylpenta-2,4-dienyl carbonate was developed.
Carbon-carbon bond formation at the more highly substituted
terminus of the pentadienyl residue was possible by introduction
of an easy to remove SiMe3 shielding group at the remote end
of the π-system. This carbonate reacted fast enough to
avoid scrambling and formation of symmetric bisallyl tetronic acids.
The 3-allyl-3-penta-2,4-dienyltetronic acid thus obtained is a key
intermediate en route to the natural spirolactone bakkenolide A.
allylation - regioselectivity - palladium - tetronic acid - Schlosser-Wittig reaction
