The rationale for this retrosynthesis is very similar to that of the first
few steps of problem 4. In addition, a nearly identical problem is found
in the last figure (5.39) in the blue book of lecture notes. But
briefly...
We again see an alpha beta unsaturated ketone which can be formed by
an intramolecular aldol condensation of A.
Analysis of A reveals the 1,5 diketone functionality that is
suggestive of a Michael reaction.
Again, of the two possible Michael reactions that could form A, the
one shown above is a better choice. The enolate is doubly stabilized,
and the disconnection offers greater simplification than in the other
case.
This Michael addition and subsequent intramolecular
aldol condensation
to form a six-membered ring is known as
the Robinson annulation, and can usually be performed in one
reaction
mixture.
More answers...
4
5
7
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