Chemistry Seminar: Visiting researcher Professor Daniel B Werz
Professor Daniel Werz
Technische Universität Braunschweig, Institute of Organic Chemistry
Carbopalladation cascades – Not only syn, but also anti
A characteristic feature of carbopalladation reactions is the syn-attack of the organo- palladium species LnX[Pd]-R on the reacting π-system. Such a step results in compounds bearing Pd and R on the same side of the originating alkene moiety. Embedded into longer domino sequences complex structures are efficiently obtained by a repetition of this syn-carbopalladation step. In this way, linear oligoynes were cyclized in a dumbbell-mode and led to benzene-type structures or higher oligoenes1
We exploited this chemistry to synthesize not only chromans, isochromans and dibenzopentafulvalenes, but also to access the most truncated π-helicenes which only consist of a Z,Z,Z,..-oligoene chain that is fixed in an all s-cis arrangement. All these domino processes are based on a syn-carbopalladation cascade.
However, a carbopalladation cascade involving formal anti-carbopalladation steps opens new avenues to create compounds with tetrasubstituted double bonds (Scheme 1). Such a process was realized, and mechanistically and computationally investigated. The synthetic potential was demonstrated for the preparation of various oligocyclic frameworks (including natural products) by making use of a variety of different terminating processes.
- E. Negishi, G. Wang, G. Zhu, Top. Organomet. Chem. 2006, 19, 1-48.
- M. Leibeling, D. C. Koester, M. Pawliczek, S. C. Schild, D. B. Werz, Nat. Chem. Biol. 2010, 6, 199.
- J. Wallbaum, R. Neufeld, D. Stalke, D. B. Werz, Angew. Chem. Int. Ed. 2013, 52, 13243.
- B. Milde, M. Leibeling, M. Pawliczek, J. Grunenberg, P. G. Jones, D. B. Werz, Angew. Chem. Int. Ed. 2015, 54, 1331.
- a) M. Pawliczek, T. F. Schneider, C. Maaß, D. Stalke, D. B. Werz, Angew. Chem. Int. Ed. 2015, 54, 4119.
b) M. Pawliczek, B. Milde, P. G. Jones, D. B. Werz, Chem. Eur. J. 2015, 21, 12303;
c) A. Düfert, D. B. Werz, Chem. Eur. J. 2016, 22, 16718; d) B. Milde, M. Pawliczek, P. G. Jones, D. B. Werz, Org. Lett. 2017, 19, 1914