2:00pm - 3:00pm|
Novel Cycloaddition Precursors for the Rapid Generation of Molecular Complexity
Abstract: Cycloaddition reactions remain a powerful tactic for the rapid generation of molecular complexity, because they often form cyclic sp3-rich chemotypes from simple and readily available sp2-containing building blocks. To this end, the continued development of cycloaddition reactions is paramount for accessing complex molecular architectures and heterocycles. Research during my graduate and postdoctoral studies has centered on the development of new classes of precursors for cycloaddition reactions and the exploitation of the products toward important applications.
In the Sarpong group, at UC-Berkeley, we discovered a novel precursor to 3-oxidopyrylium ions. Bis(1-cyanovinyl acetate) was shown to undergo an intramolecular cyclization to afford an intermediate 3-oxidopyrylium ion, which reacts with a variety of alkenes. Due to the pendant cyano group, the resulting 3-oxidopyrylium ion is highly electrophilic and primarily reacts with electron-rich olefins to obtain [5+2]-cycloadducts. These adducts could be further manipulated to generate complex polycyclic compounds; this sets the stage for accessing various natural products containing a [3.2.1]-oxabicyclooctane motif from readily available precursors.
In the Davies group, at Emory University, we are interested in the reactivity of donor-acceptor metallocarbenes. In particular, a primary thrust in the group is to use N-sulfonyltriazoles to harness and rationalize the reactivity of donor-acceptor carbenes containing heteroatom donor groups (e.g., N, and O). This would overcome a significant limitation of this chemistry, since the more established carbene precursors, those based on the diazo-functionality, are intolerant to the inclusion of heteroatoms, with deleterious side reactions predominating when such reagents are employed. To this end, we have found that 4-phthalimido-N-sulfonyl-1,2,3-triazole undergoes thermal (metal-free) cycloaddition reactions with unactivated disubstituted arenes to give dihydroindole products containing alkyl substitution at the ring fusion position in good yields. These products can be further manipulated to give valuable sp3-rich chemotypes.
|Location: ||Hutchison Hall 473 (RC)|
Posted by: Evelyn Sucy-Caffery, Chemistry, 22-Jun-17 1:52pm ET