A convenient one-pot synthesis of 4-, 6-, and 7-azaindoles from aminopyridines

Toxic Encephalopathy and Methemoglobinemia after 5-Amino-2-(trifluoromethyl)pyridine Poisoning

The aromatic amino compound 5-amino-2-(trifluoromethyl)pyridine acts as an intermediate in the synthesis of pharmaceutical products. However, the toxicity profile of this compound is sparse and no related poisoning events have been reported. Here, we report the case of a 35-year-old man who inhaled 5-amino-2-(trifluoromethyl)pyridine at work. After inhalation, the patient rapidly developed symptoms such as dizziness, fatigue, nausea, vomiting, chest tightness, and loss of consciousness. After admission, methemoglobinemia, hemolytic anemia, acute renal failure, and toxic encephalopathy occurred. Symptoms improved significantly after intravenous treatment with a low dose of methylene blue. This revealed that 5-amino-2-(trifluoromethyl)pyridine is toxic to the human body and can be absorbed through the respiratory tract, resulting in methemoglobinemia and toxic encephalopathy; thus, caution should be taken in industrial production.

Facile synthesis of 4- and 7-azaindoles from the corresponding imines by palladium-catalyzed cascade C-C and C-N coupling

The cyclization of 2,3-dihalopyridines with readily available imines provides a convenient and regioselective approach to 4- and 7-azaindoles. The regioselectivity can be controlled by the choice of the halogen atoms at the pyridine ring (chlorine versus bromine).

A general modular method of azaindole and thienopyrrole synthesis via Pd-catalyzed tandem couplings of gem-dichloroolefins

A palladium-catalyzed reaction of gem-dichloroolefins and a boronic acid via a tandem intramolecular C-N and intermolecular Suzuki coupling process gave corresponding substituted azaindoles or thienopyrroles. This method is a very modular protocol to synthesize all four isomers of azaindole and two isomers of thienopyrroles in good to excellent yield.

Microwave-Assisted Flexible Synthesis of 7-Azaindoles

7-Azaindoles are versatile building blocks, especially in medicinal chemistry, where they serve as bioisosteres of indoles or purines. Herein, we are presenting a robust and flexible synthesis of 1,3- and 1,3,6-substituted 7-azaindoles starting from nicotinic acid derivatives or 2,6-dichloropyridine, respectively. Microwave heating dramatically accelerates the penultimate reaction step, an epoxide-opening-cyclization-dehydration sequence. The functional group compatibility of the reaction is examined as well as the application of the products in further functionalizations.