Chemistry Seminar: Visiting researcher Professor Daniel B Werz

Daniel Werz chemistry seminar - event presenter


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.[1] 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[2] and dibenzopentafulvalenes,[3] 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.[4] 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.[5]

    Professor Daniel Werz scheme 1

    Scheme 1. Formal anti-carbopalladation reaction embedded in a domino cascade.