Synthesis of a diaryliodonium salt and its use in the direct arylation of andole: a two-step experiment for the organic teaching laboratory

In the past decade, C–H functionalization has been a very active topic of research in both academia and industry. When a H atom is replaced by an aryl (or heteroaryl) group, the transformation is termed “direct arylation”. This approach to the formation of key (hetero)aryl–(hetero)aryl bonds is complementary to traditional methods, such as the Suzuki–Miyaura and Stille reactions. Direct arylation/C–H functionalization is not represented in the majority of undergraduate chemistry laboratory curricula. An experiment is described here in which students carry out a multistep process, synthesizing a diaryliodonium salt and using it in the direct arylation of indole. Important organic and organometallic chemistry concepts are covered, including catalysis, traditional cross-coupling, C–H functionalization, multistep reaction processes, and regioselectivity. The experiment was successfully carried out by third- and fourth-year students in two universities over a two-year period (four times in total). Both high-yielding and low-yielding chemical steps were encountered, and a number of pedagogical approaches evolved

Exploration of C–H and N–H-bond functionalization towards 1-(1,2-diarylindol-3-yl)tetrahydroisoquinolines

The synthesis of 1,2,3-trisubstituted indoles was investigated. More specifically, straightforward synthetic routes towards 1-(1,2-diarylindol-3-yl)-N-PG-THIQs (PG = protecting group, THIQ = tetrahydroisoquinoline) employing transition metal-catalyzed C–H and N–H-bond functionalization were explored. It was found that the synthesis of the target compounds is strongly dependent on the order of events. Hence, depending on the requirements of a synthetic problem the most suitable and promising pathway can be chosen. Additionally, a new synthetic approach towards 1,2-diarylindoles starting from 1-arylindole could be established in the course of our investigation by using a palladium-catalyzed protocol. Such 1,2-diarylindoles were successfully reacted with N-Boc-THIQ to furnish 1,2,3-trisubstituted indoles as target compounds. Furthermore, regioselective N-arylation of protected and unprotected 1-(indol-3-yl)-THIQs was successfully conducted using either simple iron or copper salts as catalysts

Direct Functionalization of C−H Bonds by Iron, Nickel, and Cobalt Catalysis

Non-precious-metal-catalyzed reactions are of increasing importance in chemistry due to the outstanding ecological and economic properties of these metals. In the subfield of metal-catalyzed direct C−H functionalization reactions, recent years have shown an increasing number of publications dedicated to this topic. Nickel, cobalt, and last but not least iron, have started to enter a field which was long dominated by precious metals such as palladium, rhodium, ruthenium, and iridium. The present review article summarizes the development of iron-, nickel-, and cobalt-catalyzed C−H functionalization reactions until the end of 2016, and discusses the scope and limitations of these transformations