Silacycle-Templated Intramolecular Diels-Alder Cyclizations for the Diastereoselective Construction of Complex Carbon Skeletons.

The utility of the dioxasiline ring as a π-facial directing group in the intramolecular Diels-Alder cyclization is explored. An initial investigation of substrate scope demonstrates that the rigidity of this directing group delivers robust stereocontrol across a number of substrates, affording single diastereomers in moderate to good yields. A mechanistic investigation reveals that the reactive diene is formed through γ deprotonation followed by [1,5] hydride shifts.

Catalytic intramolecular hydroamination of aminoallenes using titanium and tantalum complexes of sterically encumbered chiral sulfonamides.

Catalysis using earth abundant metals is an important goal due to the relative scarcity and expense of precious metal catalysts. It would be even more beneficial to use earth abundant catalysts for the synthesis of common pharmaceutical structural motifs such as pyrrolidine and pyridine. Thus, developing titanium catalysts for asymmetric ring closing hydroamination is a valuable goal.