Cascade reactions are an important strategy in reaction design, allowing streamlining of chemical synthesis. Here we report a cascade Suzuki–Miyaura/Diels–Alder reaction, employing vinyl Bpin as a bifunctional reagent in two distinct roles: as an organoboron nucleophile for cross-coupling and as a Diels–Alder dienophile. Merging these two reactions enables a rapid and operationally simple synthesis of functionalized carbocycles in good yield. The effect of the organoboron subtype on Diels–Alder regioselectivity was investigated and postsynthetic modifications were carried out on a model substrate. The potential for a complementary Heck/Diels–Alder process was also assessed.
A concise strategy for the total synthesis of several Aspidosperma alkaloids is reported. A Suzuki–Miyaura
cross-coupling provides access to a 2-vinyl indole that undergoes
a Diels–Alder cascade reaction with butyn-2-one to deliver
a pyrroloindoline intermediate. This undergoes cascade amidation,
reduction, skeletal rearrangement, and intramolecular Michael addition
to provide a common intermediate containing the full framework of
the Aspidosperma alkaloids. The utility
of this intermediate is shown in the synthesis of four different natural
products.
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