Última modificación: 06/07/2017 - 15:20
El Profesor Daniel B. Werz de la Technische Universität Braunschweig, Alemania ofrecerá el próximo lunes 10 de Julio la conferencia titulada: carbopalladation cascades –not only syn, but also anti.
La conferencia tendrá lugar el próximo lunes 10 de julio a las 12:00 horas en la Sala de Grados de la Facultad de Ciencias de la Universidad de Zaragoza.
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 oligoenes.
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. 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.