ADVERTISEMENT

Gold-Catalyzed Synthesis And Reaction Pathways

Transition metal-catalyzed addition of an amine across a C-C triple bond (hydroamination reaction) represents a powerful tool for the construction of a wide range of nitrogen heterocycles.  Intramolecular hydroaminations of 2-alkynylaniline derivatives (Compound 1) to give interesting indole heterocycles (Compound 2) have been widely investigated.

Over the past decades Au, Pd, Ir, Cu, Ag and Pt catalysts have been successfully employed for this transformation, that has been carried out also in the presence of Lewis acids such as In and Zn halides. Coordination to the catalysts inverts its classical reactivity of the triple bond (that usually reacts with electrophiles) and activates it towards an intramolecular nucleophilic attack.  

ADVERTISEMENT

Compounds (Compound 3) represents a particular class of 2-alkynylanilines, bearing an electron-withdrawing group conjugated with the triple bond. Cyclization of substrates (Compound 3) through transition-metals catalyzed reactions to give indoles (Compound 4) has not been reported so far. This is probably due to the polarization of the triple bond induced by the carbonyl, that hampers the nucleophilic attack of the nitrogen to the a-carbon.

We have recently reported (Adv. Synth. Catal. 2017, 359, 3371-3377) that in the presence of highly reactive (JohnPhosAuMeCN)SbF6  (known also as Echavarren’s catalyst), an unexpected intermolecular reaction occurs, with the formation of interesting eight-membered dibenzodiazocine derivatives (Compound 5). A variety of groups R including aryl, heteroaryl, vinyl and alkyl can be introduced in the products. Moreover, esters (R = -OMe) can be used in this reaction.

 

Dibenzodiazocines represent an uncommon class of heterocycles, that is of interest in medicinal chemistry and in organometallic chemistry; in material science, copolymers containing (Compound 5) find potential application as molecular actuators. Moreover, a class of analogs of (Compound 5), i.e. Tröger’s base and its derivatives, possess a chiral cleft structure that makes them interesting scaffolds in supramolecular chemistry.

ADVERTISEMENT

The methodology described here allows an easy and efficient synthesis dibenzodiazocines with a wide range of substituents. The mechanism of the reaction has been studied: an initial intermolecular reaction affords an intermediate, that subsequently undergoes the final cyclization. Both these steps are catalyzed by the Au(I).

We hope that compound 5 will find application as precursors of new materials that can act as actuators. These are devices able convert a form of energy into motion such as light-driven molecular machines.

This study, Gold-Catalyzed Synthesis of Dibenzo[1,5]diazocines from β-(2-Aminophenyl)-α,β-ynones was recently published in the journal Advanced Synthesis & Catalysis.

Comments

READ THIS NEXT

How Asteroid Families Interact With Secular Resonances

Large asteroid families are usually the product of a collision between two bodies. Fragments of the parent body are ejected […]

Intriguing Flexible Devices Based On Mechanoluminescence

Mechanoluminescence (ML), also called triboluminescence (TL), refers to the phenomenon/process that materials could emit light under mechanical stimuli, e.g., friction, […]

Sustainable Coastal Development: Should We Care About Surface Materials?

Today, nearly half of the world’s population lives within 150 km from the coast and, in an increasingly urbanized world, […]

The “Big Bang” Of Alzheimer’s: Scientists Identify Potential Genesis of Disease

New research suggests that scientists have discovered the “Big Bang” of Alzheimer’s disease – the exact point a healthy protein […]

Fluoxetine, A Drug Used For Depression, May Adversely Affect Bones, While Another Drug, Escitalopram, Appears To Be Safer

Clinical studies provide evidence that treatment with drugs for depression increases the risk of fracture in humans. Some of these […]

Teaching Astronomy From An Early Childhood Age

In most cases, the first teachers we have in our lives are our parents. We know that a teacher’s job […]

Unearthing The Secrets Of The Lost Continent Of Zealandia

From the lost utopia of Atlantis to the brimming golds of El Dorado, there are many mythical cities and lands […]

Science Trends is a popular source of science news and education around the world. We cover everything from solar power cell technology to climate change to cancer research. We help hundreds of thousands of people every month learn about the world we live in and the latest scientific breakthroughs. Want to know more?