Tuesday April 17, 2018
"Organocatalyzed Cascade Reactions: It Is Easy Being Green"
Conventional organic synthesis entails a sequence of linear steps, in which one sets up a reaction, works up the reaction, and purifies the reaction mixture to isolate the desired product. This three step process (i.e., reaction setup, work-up, purification) is then repeated until the target molecule is attained. Aldehydes, being one of the most versatile functional groups, are often intermediates in conventional organic syntheses. It is fairly common to make use of reagents that are air/water sensitive, pyrophoric, toxic or corrosive to functionalize aldehyde intermediates. It is also fairly common to employ chiral transition metal catalysts to carry out asymmetric transformations of aldehydes.
By contrast, organocatalyzed cascade reactions combine multiple synthetic steps in a single flask, using organocatalysts, which are organic compounds that catalyze reactions. Since a work-up and purification of each discreet synthetic transformation is not required, cascade reactions can greatly reduce the time, cost and waste (i.e., solvents, silica gel) associated with organic synthesis. The development of these cascade reactions is possible because of the unique mechanisms by which organocatalysts operate, which facilitates the combination of multiple functionalizations of aldehyde substrates into a single flask. Moreover, the unique mechanisms by which organocatalysts operate also enable functionalizations of aldehyde substrates that cannot effectively be achieved using transition metal-catalyzed reactions, and without the use of conventional reagents that may be air/water sensitive, pyrophoric, toxic or corrosive. Organocatalyzed cascade reactions are therefore considered to be green chemical methods to rapidly build molecular complexity. This seminar will discuss some of our recent discoveries in this area.
~Coffee/tea will be served prior to lecture~