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Conclusions
In summary, we have demonstrated a diversity-oriented synthetic strategy based on
transition metal-catalyzed and mediated reactions of allenes (Scheme 4.56). We have gained
access to a number of structurally and functionally unique products in a relatively short number
of synthetic steps. Amino-acid derived allenes accessed via Claisen rearrangement were used as
pivotal synthetic intermediates. The Rh(I)-catalyzed allenic Alder-ene reaction of allenynes
proceeds in excellent yield affording cross conjugated trienes. These compounds were studied in
sequential cycloaddition reactions, gaining access to complex polycyclic skeletons. Furthermore,
a novel cycloisomerization of propiolamides was developed affording δ-lactams. Modified
catalytic conditions were developed to allow the synthesis of 4-alkylidene cyclopentenones.
While studying the Mo-mediated cyclocarbonylation reaction of amino-ester tethered allenynes,
a novel stereocontrol element was uncovered based on the amino-acid side chain. The knowledge
gained from these studies was used to design and synthesize a novel class of tricyclic pyrroles
via a Stetter/Paal-Knorr reaction sequence.
By modifying the substrate to include an alkene instead of an alkyne, a novel catalytic
pathway was discovered leading to the formation of tetrahydroazepines, for which mechanistic
rationale was provided. In this project we have successfully combined the goal of developing
new synthetic methodologies with providing small molecule probes for biological research. The
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