Studies on the selective hydrocarbon functionalization by development of nickel and cobalt catalysis

Abstract

1. Directing Group-Assisted C(sp3)–H Amidation via Nickel Catalysis Directing group-assisted C–H functionalization draws special attention since the process can avoid prefunctionalized starting materials compared to traditional cross-coupling reactions. However, the development of 3d transition metal catalyzed selective C–H amination in presence of competing reactive sites is still elusive. In this context, described herein is the development of Ni-catalyzed selective intermolecular C–H amidation reactions. Utilization of organic azide as both internal oxidant and amino source and electronically tuned directing group enabled selective intermolecular amidation with a broad range of carboxamides. By computational study, the intermediacy of high-valent nickel nitrenoid species was proposed and the substituent effects of directing groups on the catalytic efficiency were rationalized.

Keywords: nickel catalyst, C–H functionalization, catalyst design, organic azides, directing groups

2. Cobalt-Hydride-Catalyzed Hydrosilylation of Internal Alkynes Accompanying π-Bond Migration Selective transformation of alkynes has served as the key synthetic tools to access complex organic molecules in chemical synthesis. Recently, the development of Rh and Ru catalysis enabled π-bond migration of methylalkynes, allowing the formation of linear or branched allylic functional molecules. Utilization of electron-rich bisphosphine and electronically tailored silanes enabled catalytic isomerization-hydrosilylation cascade of internal alkynes with Co(I) hydride. This method provides the novel synthetic route to terminal branched allylsilanes otherwise difficult to prepare using the previously reported cobalt catalysis. Mechanistic studies indicate that cobalt(I)-hydride intermediates work for both π-bonds migration and hydrosilylation.

Keywords: cobalt catalyst, alkyne functionalization, catalyst design, hydrosilylation, allylsilanes