Copper-Catalyzed Alkylation of Aliphatic Amines Induced by Visible Light

Although the alkylation of an amine by an alkyl halide serves as a “textbook example” of a nucleophilic substitution reaction, the selective mono-alkylation of aliphatic amines by unactivated, hindered halides persists as a largely unsolved challenge in organic synthesis. We report herein that primary aliphatic amines can be cleanly mono-alkylated by unactivated secondary alkyl iodides in the presence of visible light and a copper catalyst. The method operates under mild conditions (–10 °C), displays good functional-group compatibility, and employs commercially available catalyst components. A trapping experiment with TEMPO is consistent with C–N bond formation via an alkyl radical in an out-of-cage process

Study of Precatalyst Degradation Leading to the Discovery of a New Ru⁰ Precatalyst for Hydrogenation and Dehydrogenation

The complex Ru-MACHO (<b>1</b>) is a widely used precatalyst for hydrogenation and dehydrogenation reactions under basic conditions. In an attempt to identify the active catalyst form, <b>1</b> was reacted with a strong base. The formation of previously unreported species was observed by NMR and mass spectrometry. This observation indicated that complex <b>1</b> quickly degraded under basic conditions when no substrate was present. X-ray crystallography enabled the identification of three complexes as products of this degradation of complex <b>1</b>. These complexes suggested degradation pathways which included ligand cleavage and reassembly, along with reduction of the ruthenium atom. One of the decomposition products, the Ru⁰ complex [Ru­(N­(CH₂CH₂PPh₂)₃)­CO] (<b>5</b>), was prepared independently and studied. <b>5</b> was found to be active, entirely additive-free, in the acceptorless dehydrogenation of aliphatic alcohols to esters. The hydrogenation of esters catalyzed by <b>5</b> was also demonstrated under base-free conditions with methanol as an additive. Protic substrates were shown to add reversibly to complex <b>5</b>, generating Ru^II–hydrido species, thus presenting a rare example of reversible oxidative addition from Ru⁰ to Ru^II and reductive elimination from Ru^II to Ru⁰