Seminar presented by Prof. Al Padwa , Emory University. Hosted by Prof. Waldemar Adam

Title: A 50 Year Infatuation/Obsession with 1,3-Dipoles and its Application Toward Bioactive Alkaloids

Albert Padwa

Department of Chemistry, Emory University, Atlanta, Georgia 30322, USA
chemap@emory.edu

The chemistry of metal carbene complexes as a method to generate 1,3-dipoles is
discussed. This approach bestows chemists with an exceptionally fertile ground for
designing and developing new stereoselective bond construction for application toward the synthesis of various bioactive alkaloids. The current activity in this area stems from the role of metal carbenes in alkene metathesis, cyclopropanation chemistry and as intermediates in an impressive array of synthetic methodology (1991CR263). The reaction of α-diazo carbonyl compounds with transition metals such as rhodium(II) carboxylates constitutes a particularly powerful method for generating synthetically useful electrophilic carbine complexes (1996CR223). Earlier work by our group has shown that the rhodium(II) catalyzed reaction of 2-diazo-3-oxobutanoates bearing tethered π-bonds represents a synthetically useful protocol for the construction of a variety of novel polycyclic skeletons (2008HCA285). The Rh(II)-catalyzed reactions of the related 2-diazo-2-(1H-indol-2-yl)acetate system has now been examined as a potential route toward scandine, a member of the melodinus family of bioactive alkaloids. Attack of the neighboring carbonyl oxygen atom onto the rhodium carbenoid center produces a cyclic 1,3-dipole that undergoes cycloaddition with a tethered alkenyl group (2008JOC2792). The resulting cycloadduct corresponds to a potential intermediate in a planned synthesis of scandine.