Carbo- and Heteropalladation Cascades

Title: 
Carbo- and Heteropalladation Cascades

Schedule: 
Date: 9 January 2023 (Monday)
Time: 5:30 PM - 6:30 PM (HKT)

Venue: 
CYPP2

Speaker: 
Prof. Daniel B. Werz
Institute of Organic Chemistry,

Albert-Ludwigs-Universität Freiburg

Abstract: 

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. More recently, we extended such cascades to initial thio- and aminopalladation steps using alkyne moieties, but also used arynes for cascade processes.

- ALL ARE WELCOME -