Direct remote c-h functionalization in piperidine derivatives
The transition metal-catalyzed direct functionalization of C-H bonds is a major research topic across the world. However selective (regio-, enantio-, diastereoselective) and efficient functionalization of C(sp3)-H bonds, remains a significant challenge: C(sp3)-H bonds are omnipresent in organic molecules and their dissociation energies are large. The use of directing groups (DGs) “guiding” the metal to specific C-H bonds and allowing intramolecular C-H bond activation, is a recognized general approach to address the selectivity challenge. However, their installation and removal add steps to the overall reaction sequence. This proposal aims to develop unprecedented regio- and diastereoselective transition metal-catalyzed functionalization of piperidine derivatives with haloalkenes making use of transient DGs, installed and removed in situ during catalysis. Access to a large number of substituted piperidines as well as known and new bicyclic scaffolds can be achieved via post-functionalization of the vinylpiperidine reaction products, making the aimed synthetic methodology potentially suitable for molecular library synthesis in drug discovery. A particularly challenging objective of the proposal is the remote (meta) functionalization with respect to the DG at C3 of the piperidine ring. Piperidine is chosen as a central heterocycle core in this application based on its importance in drug design and wide occurrence in commercial drugs (privileged scaffold).