Copper-catalyzed carbon-heteroatom bond formations : asymmetric hydroamination and continuous-flow aromatic Finkelstein reaction

Abstract

The studies presented in this dissertation are regarding the development of new methods for copper-catalyzed carbon-heteroatom bond formations, including asymmetric hydroamination and continuous-flow aromatic Finkelstein reaction. The first part of this dissertation focuses on the development of copper-catalyzed asymmetric hydroamination reactions to access various classes of enantioenriched amines. This includes the development of a broadly applicable hydroamination protocol for the synthesis of enantioenriched N-arylamines (Chapter 1) and 1,2- diamines (Chapter 2). The second part of this dissertation describes the development of copper-catalyzed aromatic Finkelstein reaction under continuous-flow conditions (Chapter 3). Part I. Chapter 1.

A Modified System for the Synthesis of Enantioenriched N-Arylamines through Copper-Catalyzed Hydroamination Despite significant recent progress in copper-catalyzed enantioselective hydroamination chemistry, the synthesis of chiral N-arylamines, which are frequently found in natural products and pharmaceuticals, has not been realized. Initial experiments with N-arylhydroxylamine ester electrophiles were unsuccessful and instead, their reduction, in the presence of copper hydride (CuH) catalysts, was observed. We detail key modifications of our previously reported hydroamination protocols that led to broadly applicable conditions for the enantioselective net addition of secondary anilines across the double bond of styrenes, 1,1 -disubstituted alkenes, and terminal alkenes. NMR studies suggest that suppression of the undesired reduction pathway is the basis for the dramatic improvements in yield under this new protocol. Chapter 2.

Regio- and Enantioselective Synthesis of 1,2-Diamine Derivatives by Copper- Catalyzed Hydroamination A highly regio- and enantioselective synthesis of 1,2-diamines using [gamma]-substituted allylic pivalamides via copper-catalyzed hydroamination is reported. The N-pivaloyl group is essential, both in facilitating the hydrocupration step and in suppressing the unproductive [beta]-elimination from the alkylcopper intermediate. This synthetic approach enables an efficient construction of chiral, differentially protected, vicinal diamines under mild conditions with broad functional group tolerance. Part II. Chapter 3. Rapid and Efficient Copper-Catalyzed Finkelstein Reaction of (Hetero)Aromatics under Continuous-Flow Conditions A general, rapid, and efficient method for the copper-catalyzed Finkelstein reaction of (hetero)aromatics has been developed using continuous flow to generate a variety of aryl iodides.

The described method can tolerate a broad range of functional groups, including N-H and O-H groups. Additionally, in lieu of isolation, the aryl iodide products in solution can be directly used in two distinct multistep continuous-flow processes (amidation or Mg-I exchange/nucleophilic addition) to demonstrate the flexibility of this method.