The importance of aromatic and benzylic amino groups in biologically active molecules is illustrated by the fact that 7 of the 10 top-selling pharmaceuticals contain such functionalities. Despite their significance, very few direct syntheses of amino-substituted compounds from unfunctionalized substrates are known; instead, indirect routes are typically used to install crucial aromatic and benzylic C-N bonds. The goal of our research is to establish broadly applicable one-step C-H bond amination methods that eliminate the need to pre-functionalize substrates. Specifically, the objective here is to establish non-directed aromatic and benzylic C-H aminations. The research is guided by the central hypothesis that novel amination rea- gents will enable these non-directed C-H functionalizations, when combined with suitable metal catalysts and ligands. The rationale of the proposed research is that the principles established for the non-directed C-H amination will be applicable to a broad variety of molecules, including complex organic molecules like most pharmaceuticals. Guided by preliminary data, the central hypothesis will be tested by pursuing two specific aims: (1) Establish Pd-catalyzed C-H aminations of arenes; and (2) establish Cu catalyzed benzylic C-H aminations. The approach to achieve these specific aims combines reagent and catalyst design as well as substrate scope studies. Experimental and computational mechanistic investigations will enable rational predictions and optimization of selectivity and reactivity. The proposed research is significant as it is expected to accelerate the discovery and synthesis of pharmaceuticals by providing more efficient, direct syntheses of amines and methods to quickly access analogues of bioactive compounds. The approach is innovative because it uses novel electrophilic amination reagents that are designed to facilitate the mechanistic understanding of non-directed C-H aminations. Furthermore, variable substructures on the amine can be introduced easily with the new reagents, providing safer, more versatile, and more practical alternatives to widely used electrophilic amination reagents like azides or Chloramine-T. Ultimately, the new methodologies have the potential to provide more efficient routes for the manufacturing of existing and future pharmaceuticals.
The proposed research will enable one-step syntheses of aromatic and benzylic amines, important functional groups in drugs and bioactive natural products. Importantly, the synthetic methodology is relevant to public health and the NIH mission, because it is expected (i) to accelerate drug discovery by rapidly accessing molecular diversity and (ii) to create shorter routes to existing drugs, which will be demonstrated by synthesizing the active pharmaceutical ingredient in Asacol(R) in two steps.
| Bandara, H M D; Jin, D; Mantell, M A et al. (2016) Non-directed aromatic C-H amination: catalytic and mechanistic studies enabled by Pd catalyst and reagent design. Catal Sci Technol 6:5304-5310 |
