Main > PHARMA. > Isoquinuclidine Core > Pyridines>Diels Alder Reactions > Org.: USA. U. (Organic Synthesis) > Report Contents

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With the help of a little electronic tug from tungsten, chemists have managed to persuade pyridines to undergo a Diels-Alder reaction. The reaction methodology offers synthetic chemists a promising new route to the complex isoquinuclidine core common to a number of medicinally relevant compounds, according to the report.

Diels-Alder reactions with pyridines are virtually unknown because the heterocycles aromatic stabilization makes them inert to this type of cycloaddition reaction. Authors, and coworkers reasoned that a PI-basic metal, like tungsten, could coordinate one of the heterocycle s double bonds and disrupt its aromaticity, effectively making the pyridine into a diene.
After coordinating to a PI-basic tungsten complex, the once-inert pyridines undergo cycloaddition with electron-deficient alkenes under mild conditions. Author s group observed that only one regioisomer of the bicyclic product is formed and that the reaction is somewhat stereoselective.

The new methodology may lead to many new reactions with p-bound heterocycles, Author points out. His group is currently trying to make the reaction general for all pyridines. "I expect that we re going to have access to a number of reactions with heterocycles that haven t been observed before," he says.






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